One day after the FBI pulled out of the probe into the cause of the July 1996 explosion of TWA Flight 800, investigators allowed reporters to view the reassembled wreckage for the first time. The wreckage, most of it resurrected from the ocean floor by divers, rises from the floor of a hangar in Calverton, N.Y., its more than 1 million parts crudely attached to metal scaffolding. "You can't look at the plane without seeing the souls of those who were lost," said James K. Kallstrom, who headed the FBI's investigation into the explosion, "and at the same time think of the strength and courage of the families of these victims." The National Transportation Safety Board has hearings scheduled next month in its effort to find a cause. The hearings may continue well into next year.