They found it quickly -- a long and thin piece of tortured metal that appeared to have been blown apart with particular ferocity. "Hey, look at this," one A.T.F. agent said. Joe Hanlin, another A.T.F. agent, knelt down and picked it up. "This is something we need to take," he said. They turned it over and discovered part of a vehicle identification number, stamped on it at the factory to help find vehicles that are destroyed in accidents, stolen or cannibalized by chop shops.

By that afternoon, the partial number -- enhanced by the F.B.I., according to an agent's sworn complaint to the court -- was put through F.B.I. computers for a "V.I.N. history check," which revealed it as an E-350 Ford Econoline van, yellow, with an Alabama license plate.

By midweek, investigators said, the van had been traced to the Ryder Truck Rental Company, one of the nation's largest leasing chains, and then in turn to a Ryder dealership on the property of Rockview Auto Sales, a used-car lot behind a chain-link fence at 1558 John F. Kennedy Boulevard, in an industrial section of Jersey City, about a mile from the Bayonne city line. The vehicles are owned by Ryder and rented by agents who receive a commission.

F.B.I. agents visited the business Wednesday, said Paul Mascitelli, the owner of Rockview. Mr. Mascitelli and others involved in the business said the agents were given the following account:

On Tuesday, Feb. 23, a slightly built man with dark hair and a neatly trimmed dark beard who was later identified as Mr. Salameh visited the office and rented a yellow Ford Econoline van for a week at the rate of $225 for the week plus 25 cents a mile. In the absence of a credit card, he put down a $400 cash deposit, showed a New York driver's license and drove off.

On Friday afternoon, Feb. 26, about two or three hours after the bombing, Mr. Salameh showed up at the dealership and said the van had been stolen the night before from the parking lot of a Shop Rite supermarket on Route 440, sometimes called "the back highway' in Jersey City, Mr. Mascitelli recounted.

He wanted his $400 back, Mr. Mascitelli remembered. Mr. Mascitelli said he asked Mr. Salameh whether he had reported the theft to the police and was told he had not. Mr. Mascitelli said Mr. Salameh needed to do that before the agency would accept his account of the loss.

"I asked him why he took so long to report it, and he said he didn't know what to do," Mr. Mascitelli said.