LAC-MEGANTIC, Quebec - Quebec police are pursuing a painstaking, wide-ranging criminal investigation of the inferno ignited by the derailment of a runaway oil train that killed at least 15 people and left dozens missing in the burned-out ruins of a downtown district.
Quebec police inspector Michel Forget ruled out terrorism as a cause, but said Tuesday that an array of other possibilities remain under investigation, including criminal negligence. Other officials have raised the possibility that the train was tampered with before the crash early Saturday.
"This is an enormous task ahead of us," Forget said. "We're not at the stage of arrests."
The heart of the town's central business district is being treated as a crime scene and remained cordoned off by police tape - not only the 30 buildings razed by the fire but also many adjacent blocks.
Investigators continued searching for the missing, fearing three dozen more bodies are buried in the downtown area closest to the tracks. The death toll rose to 15 with the discovery of two more bodies Tuesday. The bodies that have been recovered were burned so badly they have yet to be identified.
On downtown's main street - Rue de Laval - police positioned a truck near the perimeter of the no-go zone, which prevented news crews from getting direct photo and video views of the search operations being conducted by some 200 officers.
Police officials left no doubt that the hunt for the missing people was taxing - they said two officers were withdrawn from the sector because of worries about their physical condition.
"This is a very risky environment," said Quebec Provincial Police Sgt. Benoit Richard. "We have to secure the safety of those working there. We have some hotspots on the scene. There is some gas."
The Montreal, Maine & Atlantic Railway train broke loose early Saturday and hurtled downhill through the darkness nearly seven miles (11 kilometers) before jumping the tracks at 63 mph (101 kph) in Lac-Megantic, in eastern Quebec near the Maine border, investigators said. All but one of the 73 cars were carrying oil. At least five exploded.
Rail dispatchers had no chance to warn anyone during the runaway train's 18-minute journey because they didn't know it was happening themselves, Transportation Safety Board officials said. Such warning systems are in place on busier lines but not on secondary lines, said TSB manager Ed Belkaloul.
The blasts destroyed about 30 buildings, including the Musi-Cafe, a popular bar that was filled at the time, and forced about 2,000 of the town's 6,000 residents from their homes. By Tuesday, only about 800 were still barred from returning to their homes, though residents were cautioned to boil tap water before drinking it.
Efforts continued Tuesday to stop waves of crude oil spilled in the disaster from reaching the St. Lawrence River, the backbone of the province's water supply. Environment Minister Yves-Francois Blanchet said the chances were "very slim."
A few hours before the crash, the same train caught fire in a nearby town, and the engine was shut down - standard operating procedure dictated by the train's owners, Nantes Fire Chief Patrick Lambert said.
Edward Burkhardt, president and CEO of the railway's parent company, Rail World Inc., suggested that shutting off the locomotive to put out the fire might have disabled the brakes.
"An hour or so after the locomotive was shut down, the train rolled away," he told the Canadian Broadcasting Corp.
Lambert defended the fire department, saying that the blaze was extinguished within about 45 minutes and that's when firefighters' involvement ended.
"The people from MMA told us, 'That's great - the train is secure, there's no more fire, there's nothing anymore, there's no more danger,"' Lambert said. "We were given our leave, and we left."
Transportation Safety Board investigator Donald Ross said the locomotive's black box has been recovered, and the fire and the chain of events that followed were a "focal point" of the investigation.
The accident has thrown a spotlight on MMA's safety record. Before the Lac-Megantic accident, the company had 34 derailments since 2003, five of them resulting in damage of more than $100,000, according to the U.S. Federal Railroad Administration.
Burkhardt said the figures were misleading.
"This is the only significant mainline derailment this company has had in the last 10 years. We've had, like most railroads, a number of smallish incidents, usually involving accidents in yard trackage and industry trackage," he told the CBC.
Nonetheless, Burkhardt predicted the accident would lead to changes in the way railways operate, and indicated that MMA would no longer leave loaded trains unattended, a practice he said was standard in the industry.
"We want to cooperate with the town and help the residents in getting them back on their feet," Burkhardt said. "We're accepting claims that they have for their loss and ensuring nothing like this would ever happen again."
The tanker cars involved in the crash were the DOT-111 type - a staple of the American freight rail fleet whose flaws have been noted as far back as a 1991 safety study. Experts say the DOT-111's steel shell is so thin that it is prone to puncture in an accident, potentially spilling cargo that can catch fire, explode or contaminate the environment.
The derailment also raised questions about the safety of Canada's growing practice of transporting oil by train, and is sure to bolster the case for a proposed oil pipeline running from Canada across the U.S. - a project that Canadian officials badly want.
The oil on the runaway train was being transported from North Dakota's Bakken oil region to a refinery in New Brunswick on Canada's East Coast. Because of limited pipeline capacity in the Bakken region and in Canada, oil producers are increasingly using railroads to transport oil to refineries.
In Washington, White House spokesman Jay Carney said President Barack Obama's administration was closely monitoring the aftermath of the accident, and has offered assistance to Canadian officials. He said firefighters and firefighting vehicles were deployed from Maine to assist with the response, and got help from U.S. customs and border agents in making the trip.