The death toll from the massive explosion caused by a runaway oil tanker train that derailed and flattened part of a small Canadian town has risen to 13, a coroner said Monday, and dozens more remain missing.
Confirmation of eight further deaths in Lac-Megantic, in the Quebec province, came as environmental officials warned that around 100,000 liters of oil spilled in the disaster was headed for the Saint Lawrence River.
With the coroner stating that the official toll had more than doubled from the previous count of five, police at a joint press conference said around three dozen people are still missing.
Officials have said they expect the death toll to rise further given the number of people yet unaccounted for.
Evacuees meanwhile will be able to return home on Tuesday, Mayor Colette Roy-Laroche told reporters.
As many as 1,500 Lac-Megantic residents have been holed up at emergency shelters or staying with friends and family will be allowed to return to their homes.
This represents "the vast majority of residents that were evacuated," added a Quebec public safety official. They "will be allowed to go back to their homes."
About 500 people are already believed to have headed back to their homes after the smoldering debris cooled and a widening area was declared safe, the official said.
Firefighters put out the inferno late Sunday after it had destroyed a two-square-kilometer (0.77-square-mile) area of the picturesque lakeside village.
The freight train operated by Montreal, Maine & Atlantic Railway derailed and exploded early Saturday, unleashing a wall of fire that tore through homes and businesses in Lac-Megantic -- population 6,000.
The fire leveled more than four blocks, including 30 buildings, and forced about 2,000 to flee the town, which is located 250 kilometers (155 miles) east of Montreal, near the US border.
Firefighters needed more than 18 hours just to contain the inferno, the cause of which was as yet unknown.
Survivors described a wall of flames as the runaway black tanker cars jumped the tracks, just as dozens of people were enjoying a summer night out in downtown bars and restaurants.
Montreal, Maine & Atlantic Railway said in a statement that the train had been transporting 72 carloads of crude oil when it derailed.
Rail company spokesman Christophe Journet told AFP the train had been stopped in the neighboring town of Nantes, around 13 kilometers west of Lac-Megantic, for a crew changeover.
For an as yet unknown reason, Journet said, the train "started to advance, to move down the slope leading to Lac-Megantic," even though the brakes were engaged.
There was no conductor on board when the train -- en route from the US state of North Dakota to a refinery in Canada's eastern New Brunswick province -- crashed, he said.
The company speculated that a temporary "shutdown" of the train in Nantes after a small engine fire "may have resulted in the release of air brakes on the locomotive that was holding the train in place."
But it added: "We don't have complete information concerning this incident, but will cooperate with government authorities as they continue their investigation" of the disaster.
Investigators from the Transportation Safety Board of Canada examined the locomotive on Sunday and the train's equivalent of a plane's "black box" recorder has been located.
Air quality tests showed no risk to the public, as locals waited in long lines Monday morning to retrieve pets, medications and a change of clothes from those homes still standing in the cordoned-off disaster zone.
Officials said they are mostly concerned about possible contaminants in the soil, but the derailment has also put the spotlight on the challenges of transporting oil by rail.
Construction of new pipelines -- hotly opposed by environmental activists -- has been unable to keep up with surging North American oil production, and so crude is largely being shipped by rail.
According to the Canadian Railway Association, oil shipments jumped from 500 container cars in 2009 to 140,000 so far this year.
Oil shipments helped turn around Montreal, Maine & Atlantic Railway, which the daily Globe and Mail said had been hurt by slumping demand for shipping forestry products over the past decade.
The head of the Canadian Railway Association, Paul Bourque, downplayed concerns, saying that millions of cars carrying freight are transported each year by train, virtually without incident.
After flying over the nearby Chaudiere River, Quebec Environment Minister Yves-François Blanchet told public broadcaster CBC that a "very thin" oil slick now stretches nearly 100 kilometers from Lac-Megantic.
He estimated that 100,000 liters of oil spilled into the river.
Officials said it was light crude oil that could mostly be recovered with minimal damage to the ecosystem.
But for now, residents have been told not to drink the water.
Mayor Roy-Laroche, meanwhile, said she has met with Montreal, Maine & Atlantic Railway officials, as well as the town's lawyers about a possible lawsuit stemming from the disaster.