Amtrak train that derailed was going just under speed limit

An Amtrak train that derailed in rural Montana over the weekend was going just under the speed limit at about 75 mph when it went off the track along a gradual curve

JOPLIN, Mont. -- An Amtrak train that derailed in rural Montana over the weekend was going just under the speed limit at about 75 mph (121 kph) when it went off the track along a gradual curve, killing three people and possibly ejecting passengers, U.S. investigators said Monday.

Investigators do not know the cause of the accident, but they are studying video from the train and another locomotive that went over the same track a little over an hour earlier, National Transportation Safety Board Vice Chairman Bruce Landsberg said. The derailed train also had a black box that records everything happening in the train, he said.

“We have experts that are studying the camera footage frame by frame to make sure that we see exactly what the engineer saw — or maybe didn’t see,” Landsberg said.

The train derailed before a switch in the line, where one set of tracks turned into two, on a stretch of track that had been inspected just two days before, he said.