OTTAWA -- The police said on Sunday that at least five people had died and 40 were missing after runaway railroad tank cars filled with oil derailed and exploded in a small Quebec town.
"We know there will be more deaths," Lt. Michel Brunet of Quebec's provincial police told reporters in Lac-Mégantic, where the fires continued to burn on Sunday.
The derailment and explosions, which took place around 1:15 a.m. on Saturday, underscored a debate in the effort to transport North America's oil across long distances: is it safer and less environmentally destructive to move huge quantities of crude oil by train or by pipeline?
Visiting the town on Sunday, Prime Minister Stephen Harper compared it to a "war zone."
The fires, which incinerated at least 30 buildings in the core of Lac-Mégantic, a tourist town of 6,000 people about 150 miles east of Montreal, limited the work of accident investigators, as well as attempts to search for survivors and the remains of victims.
In a statement, the Montreal, Maine and Atlantic Railway said the train had been parked outside Lac-Mégantic for the night with no crew members on board. Its locomotive had been shut down, "which may have resulted in the release of air brakes on the locomotive that was holding the train in place," the statement said.
The railway did not respond to further questions, but Reuters, quoting officials from the company, said the oil aboard the train had come from the Bakken oil fields of the Western United States.
The Bakken oil deposits, which are often drilled through hydrofracking, have become a major source of oil for the railroads to move because the deposits lack direct pipeline links. Canada's oil sands producers, frustrated by a lack of pipeline capacity, are also turning to trains to ship their products.
Their move to rail comes as the Obama administration continues to weigh an application for the Keystone XL pipeline, which would deliver synthetic crude oil and bitumen, an oil-containing substance, from Alberta to refineries on the Gulf Coast. An analysis of the pipeline plan for the State Department concluded that if the pipeline was rejected, oil sands producers would instead turn to railways for shipments to the United States.
Both the Canadian National Railway and the Canadian Pacific Railway have extensive rail networks into the United States and have been promoting what the industry often calls a "pipeline on rails" to serve the oil sands. Mark Hallman, a spokesman for Canadian National, said the railway moved 5,000 carloads of crude oil to the United States from Canada in 2011, increased that amount to 30,000 carloads in 2012 and "believes it has the scope to double this business in 2013."
Unlike pipeline proposals, however, the escalation of rail movements of oil, including light oil shipments from the Bakken fields as well as from similar unconventional, or tight, oil deposits in Canada, is not covered by any regular government or regulatory review.
"We have an explosion of tight oil production in Canada and the United States, and most of it is moving by train," said Anthony Swift, a lawyer with the Natural Resources Defense Council in Washington. "But this process has happened without due diligence."
Keith Stewart, a climate and energy campaigner with Greenpeace Canada who has examined the increased use of oil trains, criticized railways in Canada and the United States for continuing to use older oil tank cars that he said were found to be unsafe more than 20 years ago.
A 2009 report by the National Transportation Safety Board about a Canadian National derailment in Illinois called the design of those tank cars "inadequate" and found that it "made the cars subject to damage and catastrophic loss of hazardous materials." Television images suggested that the surviving tank cars on the Lac-Mégantic train were of the older design.
Mr. Hallman, the spokesman for Canadian National, did not respond to questions about the safety of tank cars or the consequences of the Lac-Mégantic derailment for rail oil shipments in general. However, he said, "this tragedy notwithstanding, movement of hazardous material by rail not only can be, but is being, handled safely in the vast majority of instances." Ed Greenberg, a spokesman for Canadian Pacific, declined to comment.
The comparative safety of railways over pipelines has been the subject of much debate. Speaking in New York in May, Mr. Harper emphasized that the rejection of the Keystone XL pipeline would lead to an increase in oil sands shipments by rail, which he called "more environmentally challenging" than pipelines.
"We have seen some major safety risks associated with the crude-by-rail regime," Mr. Swift, the lawyer, said.
But Edward Whittingham, the executive director of the Pembina Institute, an environmental group based in Calgary, Alberta, said there was not conclusive research weighing the safety of the two shipment methods.
"The best data I've seen indicates," he said, "depending on your perspective, both are pretty much as safe as each other, or both are equally unsafe. There's safety and environmental risks inherent in either approach."
Accidents involving pipelines, Mr. Whittingham said, can be more difficult to detect and can release greater amounts of oil. Rail accidents are more frequent but generally release less oil. The intensity of the explosions and fires at Lac-Mégantic, he said, came as a "big surprise" to him and other researchers, given that the tank cars had been carrying crude oil, rather than a more volatile form like gasoline.
While Mr. Whittingham hopes that it will not be the case, he anticipates that proponents of the Keystone XL pipeline will use the rail accident to push their case with the Obama administration.
This article originally appeared in The New York Times.