TIJUANA, Mexico (AP) - The men flocked to the cafe under the sign with the cedar tree, symbol of their Mideast home. Here, in this alien border land, it was the beacon that led to an Arab "brother" who would help them complete their journey from Lebanon into the United States.

They would come, sometimes dozens a month over a three-year period, to find Salim Boughader Mucharrafille - the cafe owner who drove a Mercedes and catered to some of Tijuana's more affluent denizens, including workers at the U.S. consulate only a short stroll away. His American customers were unaware that the savvy boss of La Libanesa cafe ran a less reputable business on the side.

Until his arrest in December 2002, Boughader smuggled about 200 Lebanese compatriots into the United States, including sympathizers of Hezbollah, designated a terrorist organization by U.S. authorities. One client, Boughader said, worked for a Hezbollah-owned television network, which glorifies suicide bombers and is itself on an American terror watch list.

"If they had the cedar on their passport, you were going to help them. That's what my father taught me," Boughader told The Associated Press from a Mexico City prison, where he faces charges following a human-smuggling conviction in the United States.

"What I did was help a lot of young people who wanted to work for a better future. What's the crime in bringing your brother so that he can get out of a war zone?"

A report released by the Sept. 11 commission staff last year examining how terrorists travel the world cited Boughader as the only "human smuggler with suspected links to terrorists" convicted to date in the United States.

But he is not unique.

After Boughader was locked up, other smugglers operating in Lebanon, Mexico and the United States continued to help Hezbollah-affiliated migrants in their effort to illicitly enter from Tijuana, a U.S. immigration investigator said in Mexican court documents obtained by the AP.

Another smuggling network that is controlled by Sri Lanka's Tamil Tiger rebel group - a U.S.-designated terror organization - tried sneaking four Tigers over the California-Mexico border en route to Canada not long after the Sept. 11, 2001, terrorist attacks, U.S. Immigration and Customs Enforcement investigator Steven Schultz said. The four were caught along with 17 other Sri Lankans, all posing as Mexicans, attempting to enter ports at San Ysidro and Otay Mesa.

An AP investigation found these are just some of the many pipelines in Central and South America, Mexico and Canada that have illegally channelled thousands of people into the United States from so-called "special-interest" countries - those identified by the U.S. government as sponsors or supporters of terrorism.

Even when caught, illegal immigrants from those countries and other countries are sometimes released while awaiting deportation hearings, then miss those court dates, according to the AP's investigation.

The AP reviewed hundreds of pages of court indictments, affidavits, congressional testimony and government reports, and conducted dozens of interviews in Mexico and the United States to determine how migrants from countries with terrorist ties were brought illegally to the United States.

Many of the travellers, unassociated with any extremist group, genuinely came fleeing war or in search of economic opportunity. But some, once in the United States, committed fraud to obtain Social Security numbers, driver's licences or false immigration documents, U.S. court records showed.

Worse, the boldness of the smuggling enterprises, the difficulty of shutting them down and their potential to be used as terrorist conduits trouble many security officials.

Lebanese carpenter Mahmoud Youssef Kourani, smuggled in over the California border, admitted spending part of his time in the United States raising money to send back to his country to support Hezbollah - at least $40,000, according to an FBI affidavit. Kourani, court records said, told the FBI that his brother is the group's chief of military security in southern Lebanon, where Hezbollah is widely admired as a resistance force.

U.S. homeland security officials maintain they know of no cases of al-Qaida operatives using smuggling operations to enter the United States via traditional routes over the northern or southern boundaries, though they have warned that recent intelligence suggests the terror group is eyeing the borders as a way in.

"Several al-Qaida leaders believe operatives can pay their way into the country through Mexico and also believe illegal entry is more advantageous than legal entry," Jim Loy, deputy secretary of the Department of Homeland Security, told a congressional committee in February. Further, he said, "entrenched human smuggling networks and corruption in areas beyond our borders can be exploited by terrorist organizations."

The Boughader case and others show just how easy it would be - even now, nearly four years after Sept. 11.

Just weeks ago, a federal grand jury in Phoenix indicted an Iranian tailor on charges of attempting to bring illegal immigrants from his native country over the Arizona-Mexico border.

"Today they could be smuggling people, tomorrow weapons," said John Torres, deputy assistant director for smuggling and public safety investigations at Immigration and Customs Enforcement, or ICE. "The vulnerability there is a criminal or terrorist organization could take advantage of that existing infrastructure."

What the records reveal is a labyrinth of networks, which use established routes frequented for years by migrants of many nationalities.

Smugglers employ recruiters and facilitators in such "special-interest" countries as Lebanon, Jordan, Egypt, Iraq and Pakistan. One immigrant, in testimony against a now-convicted smuggler, described a "market of passports" in northern Iraq where individuals could illegally purchase documents to aid travel to America.

These smugglers use staging areas and transportation co-ordinators in such places as Quito, Ecuador; Lima, Peru; Cali, Colombia; and Guatemala City. They pay foot guides, drivers and stash-house operators in Mexico and the United States.

They have moved people by plane - into suburban Washington, D.C., Florida, California. And they have crossed clients in vehicles or on foot into Texas, New Mexico, Arizona, California and over the Canadian border, then helped deliver them to destinations across America.

They have partnered with other smugglers transporting Mexican or Central American migrants, sometimes swapping clients and transferring immigrants from "special-interest" countries and other migrants in the same loads.

"This is really a word-of-mouth business," said Laura Ingersoll, an assistant U.S. attorney in Washington, D.C., who has prosecuted at least a half-dozen smugglers who moved illegal immigrants from Egypt and Iraq into the United States.

"People from places in the Middle East will hear about who to go through, and they tend to be people from their same country, but once you get into the system we saw associations that really were driven by, 'What's the most effective way for me to move my product?"' she said. "I may call someone else and essentially sell my load to somebody who's got a boat or a truck or something going out. It's just like sacks of potatoes."

"A Mafia," is how one of Boughader's clients, Roland Nassib Maksoud, once described the business.

Maksoud, a liquor distributor, travelled from Lebanon to Mexico on a legal visa in late 2000, according to Mexican court documents. In Mexico, he said, he met two compatriots who passed along the name of a restaurateur in Tijuana who smuggled Lebanese into the United States. They had gotten the name, Boughader, from a Beirut vendor who charged them $2,000 US each for their visas to Mexico.

When Maksoud found the cafe, three Lebanese men were out front eating.

"Salim is inside," they told him in Arabic.

Boughader was meticulous about both his professions. He kept a spiral notebook with the names of his smuggling clients, their phone numbers and the date they arrived at his restaurant. In a separate ledger, Boughader told the AP, he recorded the names and numbers of his cafe customers and their favourite dishes. (AP)