LAC-MEGANTIC, Quebec — A driverless freight train carrying tankers of crude oil derailed at high speed and exploded into a giant fireball in the middle of a small Canadian town early Saturday, destroying dozens of buildings, killing at least three people and leaving an unknown number of people missing.

The disaster occurred shortly after 1 a.m. when the runaway train with 73 cars sped into Lac-Megantic, a picturesque lakeside town of about 6,000 people near the border with Maine, and came off the rails. Witnesses said the town center was crowded at the time.

Four of the pressurized tank cars caught fire and blew up in a fireball that mushroomed many hundreds of feet up into the air. The train was transporting crude oil from North Dakota to eastern Canada, likely to New Brunswick, news that is bound to revive questions about the safest way to carry the oil needed to service North America’s economies.

Witnesses said the town center, which included bars as well as stores, a library and residential streets, was crowded with weekend partygoers. The explosion destroyed dozens of buildings, many of them totally flattened, included the popular Musi-Cafe music bar, eyewitnesses said.

Canadian police announce Sunday morning that at least three people have died.

He said he could not say how people many were missing. But Industry Minister Christian Paradis, who handles Quebec affairs for the federal government, indicated the death toll was likely to rise.

“I hope there are not too many dead,” a clearly shocked Paradis told public broadcaster Radio-Canada. “It’s really terrifying. I think the worst is yet to come.”

Officials said they had few reports of injured victims, suggesting that people caught up in the blast either died on the spot or managed to escape.

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. The town is about 30 miles west of Jackman, Maine, but it’s a roundabout, 67-mile drive to get from one town to the other. Eustis is about a 42-mile drive southeast of Lac-Megantic.

‘Not sure what happened’

An official from Montreal, Maine & Atlantic, the firm that operated the train, said the train had been parked some distance away from the town and no one was on board when it derailed.

“We’re not sure what happened, but the engineer did everything by the book. He had parked the train and was waiting for his relief … somehow, the train got released,” vice president of marketing Joseph R. McGonigle told Reuters.

“There appears to be extensive damage in buildings, but we haven’t got full report yet of injuries. But we understand that there likely are some,” he said.

The rail 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 center 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 car was still burning.

Maine firefighters head to scene

Fire officials said they had asked for help from fire services in the United States. Around 20 fire engines were fighting the blaze.

Several Maine fire departments were sent to help Canadian crews deal with the blaze. Eight trucks carrying about 30 firefighters were sent across the Maine border to lend assistance, according to Franklin County dispatcher Stan Wheeler. Those trucks came from Chesterville, Eustis, Farmington, New Vineyard, Phillips, Rangeley and Strong.

“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.”

Center of town ‘almost destroyed’

Fire officials said they feared more of the tanker cars were at risk of exploding. Around 30 buildings in the town center were destroyed, some by the initial blast and others by the subsequent fire, they said.

Police imposed a 1/2-mile security zone around the blast and evacuated about 1,000 people from their homes.

“When you see the center of your town almost destroyed, you’ll understand that we’re asking ourselves how we are going to get through this event,” a tearful Roy-Laroche told a televised news briefing.

Prime Minister Stephen Harper made an initial statement via Twitter: “Thoughts & prayers are with those impacted in Lac Megantic. Horrible news.”

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 the briefing.

Montreal, Maine & Atlantic owns some 510 miles of track in Maine and Vermont in the United States and in Quebec and New Brunswick in Canada.

Fire officials said they suspected some of the remaining tanks could still be pressurized.

“We’re not sure because we can’t get close, so we’re working on the assumption that all the cars were pressurized and could explode. That’s why progress is slow and tough,” said local fire chief Denis Lauzon.

Satellite images show the railroad snaking through downtown, following a route parallel to the shore of the lake that the town is named after, before heading inland and crossing the U.S. border to the west of town.

There have been a number of high-profile derailments of trains carrying petroleum products in Canada recently, including one in Calgary, Alberta, last week when a flood-damaged bridge sagged toward the still-swollen Bow River. The derailed rail cars were removed without spilling their cargo.

BDN writer Nick McCrea contributed to this report.