Shoe-bombing suspect Richard C. Reid underwent a rigorous body check and had to remove his shoes for special screening before boarding an El Al plane this past summer, Israel's national carrier said Friday.

Even after no explosives were found, the airline considered Reid a top security risk and seated him next to an armed sky marshal in the second to last row, far from the cockpit, said an Israeli source.

A senior El Al security official, speaking on condition of anonymity, said Reid apparently flew to Israel last July to try to find weaknesses in the airline's vaunted security system, in preparation for a possible attack on an El Al flight.

On Dec. 22, the British-born Reid, 28, allegedly tried to detonate explosives on an American Airlines flight from Paris to Miami. He was overpowered by flight attendants and passengers, and the plane was diverted to Boston.

A Boston judge on Friday ordered Reid held without bail. An FBI agent testifying at the hearing said Reid was carrying a homemade bomb on the Paris-Miami flight and that preliminary tests done on his sneakers showed the presence of triacetone triperoxide, TATP, a highly volatile plastic explosive.

Authorities have been retracing Reid's travels across Europe and the Middle East and tracking his recent purchases in search of possible ties to terrorists. They said they haven't drawn any conclusions about whether Reid had accomplices. Reid's court-appointed lawyer said she knew of no evidence connecting him to terrorism.

In The Netherlands, authorities said Friday they were investigating whether Reid bought explosives and sneakers in Amsterdam.

From Amsterdam, Reid boarded an El Al flight to Tel Aviv on July 7. He spent five days in Israel, before traveling to Egypt via the Rafah border crossing at the southern end of the Gaza Strip. From Egypt, Reid apparently returned to Europe on a commercial flight, the Israeli Maariv daily said Friday.

During the pre-boarding security check, Reid aroused the suspicion of El Al ground personnel, said the airline's spokesman, Nachman Klieman, but would not elaborate on what Reid did to set off warning bells.

The El Al security official said Reid was considered suspicious because of his appearance and because he was traveling only with a hand bag.

El Al profiles passengers, and Arabs and some foreigners routinely come under closer scrutiny. Arabs, including those with Israeli citizenship, usually have their suitcases searched, and some belongings are screened individually for explosives.

Reid was subjected to a "very rigorous check of all the items he was carrying, as well as a personal search, including the removal of shoes and sending the shoes to be checked," Klieman said. "Everything he was carrying was checked."

The search did not allay suspicions and Reid was given a window seat in the back of the plane, with an armed sky marshal next to him in the aisle seat, said an Israeli source, speaking on condition of anonymity. The source said Israel had received no advance intelligence warnings about Reid.

In London, Metropolitan Police Commissioner Sir John Stevens said Friday that British police also received no word that Reid was a potential security risk.

The El Al security official said he believed Reid flew to Israel to check the airline's security arrangements, in preparation for a possible attack on a future El Al flight. "He must have dropped this plan in a hurry," the El Al official said. "It's pretty hard to smuggle weapons onto an El Al flight."

Nery Yarkoni, an Israeli aviation security consultant with clients in the United States, said the close scrutiny given to Reid indicates that profiling works. "What we see is that this guy was actually profiled as one who should be very carefully checked," said Yarkoni, a former head of Israel's Civil Aviation Authority.

Yarkoni said airport security officials must not only focus on techniques, such as trying to anticipate how suspects might try to smuggle explosives aboard a plane.

Yarkoni said blanket, intensive security checks of all passengers, regardless of the risk they pose, are not practical. "Either this will destroy the (aviation) industry or it won't prevent attacks," he said.

Retired Israeli pilot Uri Bar-Lev, who thwarted a 1970 hijacking by sending his plane diving like a free-falling elevator and knocking the hijackers off their feet, said he was pleased that passengers and crew overpowered Reid.

Bar-Lev said he believed the Sept. 11 terror attacks on New York and Washington have prompted a change in attitude, and led passengers to rely more on their own wits. "In order to prevent a hijacking or air terror, the main weapon is a state of mind that says `we are not going to be hijacked and we have to take the initiative," said Bar-Lev.

"Once you have this attitude, and this (Reid's) case just proved it, you can stop it."