The president and CEO of the railway's parent company has said an engineer failed to properly set the brakes of the train that crashed into a town in Quebec, killing at least 20 people.

Edward Burkhardt made the comments during a visit on Wednesday to the town that was devastated by the runaway oil train four days ago.

"Adequate hand-brakes were not set on this train and it was the engineer's responsibility to set them," Burkhardt, the chairman of the Montreal, Maine & Atlantic Railway, told reporters.

Canada train crash scars small community

Canadian police has opened a criminal probe into a fatal crash following claims and counter claims by operators and firefighters over the causes.

Police also raised the toll in Saturday's blast to 20 confirmed dead, with 30 more missing.

Quebec police inspector Michel Forget told a news briefing that investigators have "discovered elements" that have led to a criminal probe, but ruled out terrorism.

Investigators had focused on whether a blaze on the train a few hours before the disaster set off the deadly chain of events.

"This is a very risky environment. We have to secure the safety of those working there. We have some hotspots on the scene. There is some gas," said Benoit Richard, a Quebec police sergeant.

The bodies that have been recovered were burned so badly they have yet to be identified.

The Montreal, Maine & Atlantic Railway train broke loose early on Saturday, speeding downhill nearly 11km and jumping the tracks at 63mph in Lac-Megantic, near the Maine border, investigators said.

All but one of the 73 cars were carrying oil and at least five exploded.

The blasts destroyed about 30 buildings, including the Musi-Cafe, a popular bar that was filled at the time, and forced about a third of the town's 6,000 residents from their homes.

Source: Al Jazeera and agencies