Spurred by concerns about terrorism, federal authorities are investigating whether private guards hired by major airlines at LAX have smuggled international passengers from the Middle East and elsewhere into the United States.

Investigators with the FBI and the Immigration and Naturalization Service suspect security escorts may have helped systematically spirit away travelers en route between foreign countries under the little-known federal Transit Without Visa program, which permits foreigners to stop briefly in the U.S. without visas.

Federal authorities have expressed concerns for years about weakness in the program.

In the last three years, airlines have been cited by the INS for nearly 6,000 violations nationally in which the carriers could not document that program participants left the U.S. in a timely manner. Federal officials could not say how many of those passengers remained in the U.S.

Sporadic evidence of smuggling has cropped up before. Criminal charges were filed in recent years in New York and Los Angeles against security guards accused of helping transit passengers slip out of airports, records show.

A report by the Justice Department inspector general after the Sept. 11 attacks warned of continuing gaps in the transit program and concluded that the agency "must take immediate action ... to enhance national security."

Federal law enforcement sources say their inquiry at Los Angeles International Airport has yet to turn up evidence that violent extremists have gotten into the country via the transit program. "We are not far enough into the investigation to know if it has been exploited by terrorists," one source said.

Agents, however, are aggressively tracking down hundreds of clients--most of them Middle Eastern--of a phony-document ring that may be linked to the suspected airport-smuggling scam. Investigators suspect some of those who bought bogus Social Security cards fro m the ring arrived at LAX as transit passengers and remained in the country illegally. A former LAX transit guard from Jordan--who obtained an INS stamp--is among those who pleaded guilty in the false-document ring.

Airlines vigorously defend the decades-old Transit Without Visa program as both safe and economically vital. But leading INS officials say the threat of terrorism demands a re-examination.

"To some extent, this comes down to us taking a new and different look at everything we do after Sept. 11," said Thomas J. Schiltgen, INS district director in Los Angeles.

The INS suspended much of the program immediately after last September's attacks, and agency officials considered eliminating it. However, the program was revived in November after some changes, including a new requirement that all transit passengers undergo immigration inspection, which includes a check against federal databases that flag suspected criminals and potential terrorists.

The INS is expected to propose a broader overhaul soon. Among other changes, the agency is considering a ban on multiple stops for transit passengers and adding several Middle Eastern and African countries to a list of more than 20 nations whose citizens are barred from passing through U.S. airports without visas.

The Transit Without Visa program is an important marketing tool abroad for the highly competitive airline industry. In the three most recent fiscal years, more than 5 million airline travelers--almost 5% of all foreign nationals entering the United States via airports--arrived as visaless transit passengers, destined for connecting flights overseas.

The program allows carriers to route many of their most lucrative customers through LAX and other major hubs in the U.S., while offering fliers a means to avoid the inconvenience of obtaining visas, including time-consuming State Department background checks.

Once in the United States, transit passengers typically remain in the airport for several hours. More than 1 million a year are directed to secured lounges. But those lounges are sometimes poorly guarded, according to the post-Sept. 11 critique by the Justice Department's inspector general.

Some Without Visas Leave Airports

An additional 200,000 passengers a year, escorted by private guards, are allowed to mingle with the general airport population, transfer to other terminals or even leave the airport. Some visit restaurants, hospitals or consulates, or stay overnight in hotels while waiting for their connecting flights.

Air carriers, under contract with the INS, are responsible for providing the escorts and ensuring that the travelers depart within eight hours or on the next available flight. LAX is the nation's leading port of entry for the escort program, with 56,000 travelers served in fiscal 2001.

Federal studies dating back almost a decade have warned that the program is outdated and vulnerable to abuse. Moreover, according to records and interviews, the INS cannot verify that all the foreign travelers actually leave--largely because inspectors at airports do not confirm each departure at the time of boarding, but rely on an archaic paperwork system that takes weeks to enter into INS computers.

INS officials acknowledge gaps in the system. In one LAX case two years ago, two employees of a security firm pleaded guilty to federal charges for trying to smuggle in three Thai women who arrived as transit passengers on a Korean Air flight from Seoul.

The scheme, foiled by the employees' supervisor, involved swapping the women--allegedly destined for employment at a massage parlor--with three impostors who were to take their outbound seats.

Sources say the current federal investigation of the program at LAX involves a review of airport operations, a hunt for transit passengers who may have slipped into the country in recent years, and an effort to identify corrupt airport workers who may have aided them.

Directing the investigation, officials said, is an a nti-terrorism task force--including representatives from the FBI, INS, Federal Aviation Administration and Social Security Administration--that is focusing on long-term national security issues such as immigration.

The LAX investigation stems in part from the prosecution of the phony-document ring, which generated nearly 1,000 fraudulent Social Security numbers, mostly for Middle Easterners. The operation was broken up in early 2000.

After the World Trade Center and Pentagon attacks, federal agents stepped up efforts to find the cardholders, who have scattered across the country and overseas.

Among the three ring members who pleaded guilty in the case was Firas Rteimeh, a 32-year-old Jordanian who worked as a transit escort at LAX from 1996 until shortly before his arrest.

Rteimeh was employed by Aviation Safeguards, the largest of about half a dozen providers of transit passenger security services at LAX. The company, under contract with various airlines, escorts 50 to 60 transit passengers a day at LAX, according to interviews.

Rteimeh, who recently completed his 18-month sentence and is free pending an appeal that could affect INS efforts to deport him, helped line up customers for the fake Social Security cards, court records show. Agents found more than $100,000 in cash and the INS stamp during a search of his apartment.

Rteimeh and his attorney did not respond to interview requests. In a brief conversation in March, Rteimeh said he was not aware of a continuing investigation.

Aviation Safeguards has not been advised of a federal probe of the transit program, said Sunny Williams, the company's Los Angeles general manager. "If they are investigating our employees, I don't know," Williams said in an interview. "[But] we handle quite a few of these types of escorts, [so] I wouldn't be surprised."

Workers Disciplined if Departures Not Proved

Aviation Safeguards, a division of Command Security Corp. of New York, is a major nationwide airport security provider. Two years ago, a branch of the company in Florida was placed on two years' probation and ordered to pay more than $100,000 in fines and restitution after a former general manager allowed more than 20 employees to work in secure airport areas without required background checks.

At LAX, Williams said, Aviation Safeguards assisted with the Social Security fraud investigation, adding, "We will cooperate in the fullest" with the current inquiry.

The executive said he had no suspicions about Rteimeh but he acknowledged he has had to discipline or terminate workers in recent years because airlines could not document that escorted passengers actually departed.

"Has it happened to our company? Yes," Williams said. "Occasionally, we've had people who are bad apples and we got rid of them.

"Any [transit security company] who says the contrary is lying."

Several federal officials say Rteimeh was investigated more than two years ago, while still working as a guard, by the INS on suspicion of smuggling in fellow Jordanians via the transit program. He was never charged in that case.

The Transit Without Visa program was launched after World War II to help resettle refugees, many of whom lacked identity and travel documents.

INS officials have argued that the program is obsolete and represents too great a security risk. But drawn out legal and policy battles between the INS and the airline industry have delayed some efforts to bolster controls.

Airline representatives, struggling to recover from the travel slump after Sept. 11, say they will lose millions of dollars in revenue and about 40% of international passengers transiting through U.S. airports if visas are required for all such travelers. Likely to be especially hard hit, industry officials say, would be giant U.S. carriers such as American and Continental, with extensive routings between the U.S. and Asia, Europe and Latin America.

"There are people in the INS who feel that the Transit Without Visa program has been nothing but an open invitation for people to enter the United States illegally," said Robert Davidson, assistant director of facilitation services for the International Air Transport Assn. "The numbers, I don't believe, support that. But, for some, if you lose one person, that's too many."

The inspector general's report issued in December found that security concerns identified nine years ago in the transit passenger program "for the most part ... still exist today."

Although it does not identify airports or airlines, the report found that security standards for transit passengers vary nationwide.

In some airports, INS managers reported, transit passengers have been allowed to move unaccompanied. Passenger-to-guard ratios vary, with as many as 20 travelers per escort. In addition, INS managers told federal investigators, some airlines are willing to absorb a $500 fee for each passenger they cannot prove exited the country on time, viewing the payments as a cost of doing business and cheaper than beefing up security.

"The onus is on the airlines, and that makes it in some cases problematic," said Peter Gordon, the INS' assistant regional director for inspections in the western states. "But it's a very important privilege for these airlines. It's an important source of profit. So they guard it jealously."

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Times staff writer Robert J. Lopez and researcher Jacquelyn Cenacveria contributed to this report.