The operator of a train that rolled downhill and careened into a Quebec town, causing a deadly explosion, said on Sunday that the air brakes used to hold the locomotive in place may have been released after the train was parked.
The train had been hauling crude oil from North Dakota to eastern Canada, and was sitting parked, without a driver, outside town when it began to roll downhill, gathered speed and derailed on a curve at 1 a.m. (0500 GMT) on Saturday.
The statement from Montreal, Maine & Atlantic Railway did not make clear how the brakes had been disengaged, or who could be responsible.
"One fact that has emerged is the locomotive of the (parked) oil train ... was shut down subsequent to the departure of the engineer who had handled the train from Farnham, which may have resulted in the release of air brakes on the locomotive that was holding the train in place," the company statement said.
Montreal, Maine & Atlantic Railway, a small operator with some 500 miles of tracks in New England and eastern Canada, had said an engineer had correctly secured the train for the night.
Five people died and 40 are missing after the train, which was carrying crude oil, hurtled into the center of Lac-Megantic, jumped the tracks and exploded.
Montreal Maine & Atlantic said it had not been able to complete its own investigation while the Canadian government was probing the cause of the blast. It said a dozen company officials are in Lac-Megantic.