One person has been confirmed dead and scores are missing after a runaway freight train in Canada crashed, causing a huge fireball.
Around 1,000 people have been evacuated and a 1 km exclusion zone has been declared with fears more wagons could explode.
The accident occurred shortly after 1 am local time Saturday (0500 GMT) when the driverless train with 73 oil wagons sped into Lac-Megantic.
It came off the rails in the centre of the picturesque lakeside town with a population of around 6,000 people near the US border with Maine.
Witnesses said the town centre was crowded at the time.
Four of the wagons caught fire and sparked a massive fireball which mushroomed high into the air.
The train was carrying crude oil from North Dakota to New Brunswick.
Although police said they could not yet get close enough to determine the number of victims from the still-burning fires, an aerial photograph showed flattened buildings in the town centre.
The railway operator - Montreal, Maine & Atlantic - said the train had been parked some distance from the town and no-one was on board when it derailed.
A spokesman said the driver had followed the correct procedures in parking the train while waiting for a relief colleague but that the train somehow 'got released'.
Police said some people had been unable to reach missing family or friends by phone, but they declined to say how many people might be missing.
The railway tracks pass next to a bar popular with young people. Eyewitness Yvon Rosa said he had just left the bar when he saw the train speeding into the middle of the town.
"I have never seen a train traveling that quickly into the center of Lac-Megantic," he told French-language broadcaster Radio-Canada, saying he watched as the train hurtled around a bend.
"I saw the wagons come off the tracks ... everything exploded. In just one minute the centre of the town was covered in fire."
Residents told reporters they had heard five or six large blasts. Nearly 12 hours after the derailment, one rail wagon was still burning.
"Many parents are worried because they haven't been able to communicate with a member of their family or an acquaintance," Mayor Colette Roy-Laroche told Radio-Canada.
"We can't give out any information on what's happening right now because the firemen haven't been able to get close."
CENTRE OF TOWN 'ALMOST DESTROYED'
Fire officials said they feared more tanker cars were at risk of exploding. Around 30 buildings in the town centre were destroyed, some by the initial blast and others by the subsequent fire, they said.
"When you see the centre of your town almost destroyed, you'll understand that we're asking ourselves how we are going to get through this event," a tearful Mayor Roy-Laroche told a televised news briefing.
Canadian Prime Minister Stephen Harper made an initial statement via Twitter: "Thoughts & prayers are with those impacted in Lac Megantic. Horrible news."
Lac-Megantic is part of Quebec's Eastern Townships region, an area popular with tourists that is close to the border with Maine and Vermont. Quebec is a predominantly French-speaking province in the eastern half of Canada.
Fire officials said they had asked for help from fire services in the US. Around 20 fire engines were fighting the blaze.
Police said some of the tanker cars had spilled their contents into the river that runs through the town.
"I can say absolutely nothing about victims... We've been told about people who are not answering their phones, but you have to understand that there are people who are out of town and on holiday," police spokesman Michel Brunet told a briefing.