BRIDGEPORT -- After a day of combing through the wreckage of two trains that collided during Friday evening's rush hour, federal investigators have found a broken rail, but they do not know if it was a factor in the eastbound train's derailment.

Federal investigators combed through Metro-North train wreckage Saturday in what promises to be a lengthy investigation into the cause of Friday night's rush-hour collision.

National Transportation Safety Board staffers pulled up in a caravan of cars along Commerce Avenue, joining an awaiting group of state and city officials for a mid-morning tour of the crash scene.

NTSB member Earl Weener told reporters the probe is focusing on the train's brake performance, condition of wheels, condition of tracks and signals.

"We'll also be looking at how the crew behaved (and) operated the train," Weener said.

He said data recorders should have been on board both trains, collecting their rate of speed and other information.

The goal is not only to determine what happened, he said, but seek to prevent it in the future.