The engineer of a commuter train that derailed, killing two passengers, told investigators that he continued traveling at nearly 70 mph because he saw no signals indicating he was supposed to switch tracks, a union official said Tuesday.

"He said that he saw all clear signals, and that would have allowed him to operate at maximum track speed of 70 mph," said Rick Radek (search), a vice president of the Brotherhood of Locomotive Engineers and Trainmen (search). "That's what he was doing."

The train was traveling at 69 mph but federal officials said it should have been going no faster than 10 mph when it switched tracks and derailed about 5 miles south of downtown Chicago on Saturday. Besides the two dead, 80 passengers were injured.

National Transportation Safety Board (search) officials have said the signals appeared to have been working properly, which should have prompted the engineer to slow as he approached the crossover.

Radek said union officials have advised the engineer not to discuss the case with anyone other than NTSB investigators.

The investigators conducted test runs Tuesday along the stretch of track in an effort to reconstruct what the engineer experienced just before the derailment. At several spots, investigators measured distances between the train's control cab and the trackside signals.