Canada runaway train: Lac-Megantic death toll rises
Police are trying to account for dozens of missing people - popular bars near the blast site were said to have been crowded at the time.
"People have been reported missing or disappeared but... we are not going to issue a figure," police spokesman Michel Brunet told reporters.
"We know there are going to be more deaths."
Local media have reported up to 100 people missing, but police are checking whether people reported missing were simply away on holiday.
'It's a mess'
Two of five cars that exploded are still ablaze nearly 36 hours later, Lac-Megantic Fire Chief Denis Lauzon told reporters on Sunday morning.
Firefighters have been battling the flames with water and a fire retardant, but are staying at least 1,000 ft from the burning tankers for fear of more blasts, he added.
Fire Chief Denis Lauzon: "We still have a risk of explosions as we still have tankers on fire"
About 30 buildings - including some of the town's most historic structures - were obliterated by the blast.
"We lost the bibliotheque [library] which had all the memories of people here - it's a mess," said Chief Lauzon.
The train's 73 cars carrying pressurised containers of crude oil reportedly uncoupled from an engine parked outside the town around 01:00 (06:00 BST) on Saturday, gathering speed as they rolled down the tracks before derailing in Lac-Megantic.
Eyewitnesses said that by the time the cars reached the town they were travelling at considerable speed.
Bernard Demers, who runs a restaurant near the blast site, said the fireball that followed the derailment was "like an atomic bomb", the Sunday Telegraph reported.
The Montreal, Maine & Atlantic train had five locomotive engines and 73 cars filled with light crude oil, and was parked in the village of Nantes - about 7km (four miles) from Lac-Megantic - during an overnight driver shift-change, said a company spokesman.
An engineer had parked the train and put the brakes of its five locomotive engines on "properly" before going to a local hotel for the night, said the spokesman, Joe McGonigle.
The cars filled with fuel somehow became uncoupled, causing them to roll downhill into the town and derail, he added.
A one-kilometre exclusion zone was set up amid fears of more pressurised containers exploding.
The train was carrying the crude oil from the Bakken Field in North Dakota. Montreal, Maine & Atlantic owns more than 800km (500 miles) of track serving Maine, Vermont, Quebec and New Brunswick.
A lakeside town that is home to some 6,000 people, Lac-Megantic is close to the US border with Vermont and 130 miles north of Maine's capital, Augusta.
Source: BBC NEWS