Witnesses at the World Trade Center bombing trial Wednesday established the first link between the twisted and charred wreckage of an explosive-laden vehicle and a yellow Ryder van reputedly rented by one of four defendants.

The milestone in a trial marked by weeks of tedious testimony accompanying the introduction of scores of scraps of bomb-wracked vehicle parts came quietly.It happened as a gray-haired veteran investigator pointed to a blowup of a computer printout and matter-of-factly explained the process of using a vehicle identification number to make the link.

William Fritz, a field agent of the National Insurance Crime Bureau, told how he was called to the twin towers by the FBI five days after the Feb. 26 bombing that killed six and injured 1,000.

The investigator said he was able to positively identify a piece of the wreckage through a partial vehicle identification number found on a metal frame. That information identified the make model and year of the vehicle and through its registration that it was owned by a Ryder agency in Jersey City, N.J.

The prosecution has charged that Mohamad Salameh, 25, rented a yellow Ford Econoline from the rental agency but reported it stolen the day before the bombing. He was arrested when he returned for a refund after the bombing.

The government maintains it was that van filled with a 1,000-pound homemade bomb that exploded at the trade center.