CHICAGO (AP) — An Amtrak train was going about 25 mph over the speed limit — despite a signal indicating another train was on the same track — moments before it hit a stationary freight train Friday, injuring dozens of people, federal officials said Sunday.

The Amtrak train's engineer told investigators he realized the speed limit was 15 mph in that stretch of track but accelerated to 40 mph anyway, National Transportation Safety Board Vice Chairman Robert Sumwalt told reporters.

The speed limit on that portion of track, which is usually 79 mph, had been reduced to 15 mph by a red and yellow "restricting signal," indicating another train was on the track, the official said.