LAC-MEGANTIC, Quebec Investigators seeking the cause of the deadly train crash in the tiny Quebec town of Lac-Megantic, were focusing Tuesday on the train's brakes, the railway company's own regulations and whether Canada needs tougher train-transport standards.
Officials from the Transportation Safety Board of Canada said more than a dozen investigators were examining every angle of the accident, in which a runaway train hauling 72 cars of crude oil plowed into the lakeside town and exploded.
About 50 people are either confirmed dead, or are still missing, likely turning the accident into North America's worst rail disaster since 1989.
But TSB investigators have not yet been able to enter the "red zone", where the tracks ran through the centre of the lakeside town, and where the derailment and explosion levelled buildings and left most of the rail cars in a huge, ungainly clump.
One of the key elements of the probe, which lead investigator Donald Ross said is still in its very early stages, is the strength of the widely used DOT-111 cylindrical tanker cars that carried the crude. Both the TSB and its U.S. equivalent, the National Transportation Safety Board, have long urged tougher rules for such cars.
"If we think there needs to be a safety message out to the industry that they need to beef things up, we're going to do it," Ross said.
But nobody knows if stronger cars would have prevented the disaster, which involved a train that Ross said was travelling "well in excess of its authorized speed".
Some 2,000 residents of Lac-Megantic, or one third of the town's population, were asked to leave their homes after the accident. Moore than half were allowed back for the first time on Tuesday, although 50 factories and businesses in the blast zone remain shut.
With fires out and authorities now able to get to the epicentre of the blast, the death toll is expected to climb.
"They know their loved ones were there, on the site. Most of them are now waiting for confirmation - because that makes it official," said Steve Lemay, the parish priest of Lac-Megantic, who has been meeting with affected families. "It's clear that they are not waiting for the missing to return."
The coroner's office asked relatives of the missing to bring in brushes, combs and razors so specialists could extract DNA samples from strands of hair.
BALL OF FIRE
The train was parked in nearby Nantes, Quebec, on Friday night when one of its engines, which had been left running to ensure the air brakes had enough pressure, caught fire. Local firemen turned off the engine, put out the fire and went home.
The unattended train then started moving downhill toward Lac-Megantic, and derailed and blew up in the town centre at just after 1 a.m. (0500 GMT) on Saturday. The ensuing fire engulfed nearby buildings.
Train operator Montreal, Maine & Atlantic says shutting off the engine caused the brakes to lose pressure, sending the train into the town. But the company's chairman, Ed Burkhardt, also said the company will no longer leave trains unattended or change crews at Nantes, near Quebec's border with Maine.
"They're going to go right through there and change crews at another station further west and where the terrain is better and where the infrastructure is better," he told the Canadian Broadcasting Corporation. "Infrastructure was not a factor in this derailment but it's always a consideration."
Ross said the train was on a 1.2 percent grade when it started sliding toward Lac-Megantic, a relatively steep grade in railroad terms.
He said the train line did not have a signal system that could have warned the dispatcher of a runaway train, and that although all trains are required to have automatic braking systems for runaways - called dead man switches - they only work when the train's locomotives are running.
Industry rules say engineers must set enough of a train's handbrakes to ensure it cannot move. Ross said his team would not be able to check whether the brakes were set until it is allowed to enter the centre of town and look closely at the pile of derailed cars.
Burkhardt told Reuters the company had followed protocol, using the same standard as Canadian Pacific Railways, Canada's No. 2 railroad.
By Monday evening, the emergency crews had finally reached the Musi-Cafe, a downtown bar near the epicentre of the blast. A band was performing there and the building was packed with people when the explosion occurred, eyewitnesses told Reuters.
"I don't know how many friends I lost that night," said Jean-Sebastien Jacques, 24, who was walking toward the Musi-Cafe at the time of the accident. "We have looked at the shelter and around town, but that bar was full when the train hit."
(Writing by Janet Guttsman and David Ljunggren; Editing by Eric Walsh, Paul Simao and Peter Galloway)