Canadian police have struggled to find the remains of people killed when a driverless crude oil train derailed and blew up in a small Quebec town over the weekend as questions grew over how the disaster had occurred.
The five locomotives and 72 oil cars had been parked about 13 km from Lac-Megantic on Friday night. The brakes then somehow released and the train gathered pace as it rolled down a hill into the centre of the town early on Saturday morning.
It derailed and exploded into a gigantic fireball, flattening dozens of buildings and killing five people. Another 40 are missing and few residents hold out hope that they will be found alive.
Police said on Monday they had been unable to examine much of the town centre overnight because the area was still too dangerous.
Dozens of tanker waggons, some of them destroyed, are lying at the accident site.
"It's an area that is still extremely risky ... The fire service decided they could not allow us to go there for security reasons. We'll see what we can do today," police spokesman Benoit Richard told reporters on Monday.
One of the destroyed buildings was a music bar popular with young people.
Lac-Megantic, a lakeside town of 6,000 ringed by forests of pine and birch, is in the predominantly French-speaking province of Quebec, close to the border with Maine and Vermont. About 2,000 people were evacuated.
None of the dead have been identified. Two of the badly burned bodies recovered so far have been sent to Montreal for identification and the other three will be transported there later on Monday, the coroner's office said.
Canada's Transportation Safety Board, which is probing the disaster, has retrieved the train's black box data recorder and a separate device that contains details of the braking system.
The train - operated by the Montreal, Maine & Atlantic Railway - had been parked at Nantes, 13 km to the west of Lac-Megantic, late on Friday night.
Company chairman Ed Burkhardt said the engineer had shut down four of the five locomotive units on the train, a standard procedure, before heading to Lac-Megantic to sleep.
Somehow, he told the Toronto Star, the fifth locomotive was also shut down.
"If the operating locomotive is shut down, there's nothing left to keep the brakes charged up, and the brake pressure will drop finally to the point where they can't be held in place any longer," Burkhardt said.
Montreal Maine & Atlantic is one of many North American railroads that have vastly stepped up shipments of crude oil as pipelines from North Dakota and from Canada's oil-producing areas fill to capacity, and the accident is bound to raise concern about the practice.
Adding to the mystery is the fact that after the train was parked on Friday night, a part of it caught fire. Local firemen were called to put out the blaze.
It was not clear if the actions of the firemen could be linked to the derailment.
In Nantes, a shopkeeper who would not give her name said locals were often irritated by trains being parked while still running their engines but said she had never heard of any cases in the town of vandalism on the tracks.
"This, for our small community, is an accident like 9/11," she told Reuters.