The head of the US railway company whose runaway oil train crashed into a Quebec town blamed the engineer today for failing to set the brakes properly.

The train hurtled down an 11km incline, derailed and ignited a fire that killed at least 15 people and left dozens missing.

Rail World Inc CEO Edward Burkhart said the engineer has been suspended without pay and was under police supervision.

Until today, the railway had defended its employees' actions, but that changed abruptly as Mr Burkhardt singled out the engineer as culpable.

He said the engineer was "under police control."

Mr Burkhardt said: "He's not in jail, but police have talked about prosecuting him," the CEO said. "I understand exactly why the police are considering criminal charges ... If that's the case, let the chips fall where they may."

50 people dead or missing after the oil-tanker train exploded in the Quebec town of Lac-Megantic.

200 investigators sifted through the charred wreckage of what they said is a crime scene.

The runaway train derailed and blew up in the middle of the town of 6,000 near the Maine border early last Saturday morning.

The crash flattened dozens of buildings in Lac-Megantic's historic downtown and it looked like a war zone.

As investigators search for clues in what could turn out to be North America's worst railway disaster since 1989, Quebec police have made it clear that the figure for those missing includes the dead.

None of the 15 bodies they have found has been identified and few residents hold out hope that any of the missing will be found alive.

Montreal Maine & Atlantic Railway, which owns the track through Lac-Megantic and operated the tanker train, is one of many North American railroads that have vastly stepped up shipments of crude oil.

Oil producers are seeking alternatives to pipelines that have been stretched to capacity by higher output in Canada and North Dakota.

Canada's Transportation Safety Board wants to know if the operator followed proper safety procedures in the hours before the unmanned 72-car train rolled down a hill and slammed into Lac-Megantic.

The incident forced about 2,000 people, roughly a third of the town's population, to leave their homes and seek shelter in local schools or with friends and family.

Around 1,200 have since been allowed to return to their homes, some of which are still without power or water.

Lac-Megantic is about 255km east of Montreal and close to the border with Maine and Vermont.

MMA executives have said they believe the train's air brakes failed after local firefighters shut down the engine on one of its locomotives late on Friday night to put out a fire.

At the time the train was parked in the neighboring municipality of Nantes, uphill from Lac-Megantic.

But it is not clear if the train's engineer set enough hand brakes,  which are meant to hold a train in place even if the air brakes fail, before he left the train for a shift change shortly before the fire broke out.

MMA, which is headquartered in Chicago, has a long history of accidents in Canada.

According to Transportation Safety Board data, there have been 129 accidents, including 77 derailments since 2003.

It is one of only two rail companies in Canada that is allowed to operate trains manned by a single engineer.