LAC-MEGANTIC, Que. -- First came the unusually loud rumble of a rapidly approaching train, then came the thunderous crash that had terrified patrons at the nearby bar scrambling for their lives.

Then came the wall of fire, recalled Bernard Theberge, one of the people who bolted Saturday from the Quebec watering hole.

"It was like a movie," said Theberge, who considered himself fortunate to escape with only second-degree burns on his right arm.

"Explosions as if it were scripted -- but this was live."

At least one person died after a train derailment set off several massive explosions in the heart of Lac-Megantic, a blast that destroyed buildings and sent spectacular fireballs dozens of metres into the sky. The tanker rail cars were carrying crude oil.

Many people are thought to be missing.

As the fires continued to rage late Saturday, limiting access to the area, police indicated that they expected the death toll to rise.

"We do expect we'll have other people who will be found deceased unfortunately," Lt. Guy Lapointe, a spokesman with Quebec provincial police, told a news conference.

"We also expect that down the line ... there will be more people reported missing than people actually found dead."

Lapointe refused to give any estimate of people unaccounted for because emergency crews still cannot reach a two-kilometre-squared section of the town out of concern that five more tankers could still explode.

The cause of the accident is believed to be a runaway train, according to the railway's operator.

The president and CEO of Rail World Inc., the parent company of Montreal, Maine & Atlantic Railway, said the train was parked uphill of Lac-Megantic before the incident.

"If brakes aren't properly applied on a train, it's going to run away," Edward Burkhardt told The Canadian Press.

"But we think the brakes were properly applied on this train."

Burkhardt, who indicated he was mystified by the disaster, said the train was parked because the engineer had finished his run.

"We've had a very good safety record for these 10 years," he said of the decade-old railroad.

"Well, I think we've blown it here."

Responding to a reporter's question during Saturday's news conference, Lac-Megantic's fire chief confirmed that firefighters in a nearby community were called to a locomotive blaze on the same train a couple of hours before the derailment. Denis Lauzon said he could not provide additional details about that fire since it was in another jurisdiction.

The multiple blasts came over a span of several hours and wiped out some 30 buildings. Locals say that many are still unaccounted for in the town of 6,000, about 250 kilometres east of Montreal.

Theberge, who was outside on the bar's patio at the time of the crash, feared for the safety of those inside the popular Musi-Cafe when the first explosion went off shortly after 1 a.m.

"People started running and the fire ignited almost instantaneously," he said.

"It was like a wall of fire with intense heat."

Witnesses said the eruptions sent many stunned locals darting through the streets under the powerful heat of towering fireballs and a red glow that illuminated the night sky.

Between 1,500 and 2,000 people were forced from their homes as authorities set up a wide security perimeter around the town. Officials have expressed concern about poor air quality in the area from the smoke.

Several tankers from the train of more than 70 cars exploded in the downtown core, a popular area that is often busy on summer weekend nights. It's also a district that many here called home.

After the explosions and fire tore through the centre of town, many buildings were gone, almost as if they had vanished. Lines of tall trees in the area looked like giant standing matchsticks, blackened from bottom to tip.

Asked by a reporter what the scene looked like up close, Lauzon summed it up: "A war zone."

Flames and billowing black smoke could be seen throughout the day Saturday, as firefighters doused the blaze for hours.

"The Metro (grocery) store, Dollarama, everything that was there is gone," said resident Claude Bedard.

Dozens of locals stood on the main drag leading into the downtown area, hours after the explosions. Many locals had been awake much of the night, after the area shook from blasts that one man initially thought was a "nuclear" bomb and shot flames higher than the steeple of a nearby church.

They stared down the straight street from behind the orange tape. Less than a kilometre down Rue Laval a railway tanker sat at the edge of the road as flames danced around it.

Many of them feared the worst.

"On a beautiful evening like this... there were a lot of people there," said Bernard Demers, who owns a restaurant near the blast site.

"It was a big explosion. It's a catastrophe. It's terrible for the population."

Demers, whose home was evacuated, described the scene in town overnight.

"Early this morning (there was) a big explosion like an atomic bomb," said Demers, who has lived in Lac-Megantic for 45 years.

"A beautiful town but now it won't be the same."

Charles Coue said he and his wife awoke to the explosion, which went off a couple of hundred metres from their home.

"(We felt) the heat," said Coue, who sprinted from his house with his wife amid the panic.

"It went boom and it came like a fireball."

A Facebook group was quickly set up to help people track down loved ones who couldn't be reached by phone.

A woman offering to locate people at an emergency centre set up at the local high school received hundreds of requests for help.

Several neighbouring municipalities, including Sherbrooke and Saint-Georges-de-Beauce, were enlisted to help Lac-Megantic deal with the disaster.

Emergency services south of the border were also lending a hand, including a fleet of fire trucks deployed from northern Maine, according to a spokesman at the sheriff's office in Franklin County.

A large but undetermined amount of oil from the tankers also spilled into the Chaudiere River.

Environment Quebec spokesman Christian Blanchette said the cars were filled with crude oil and that four were damaged by fire and the explosions.

"Right now, there is big smoke in the air, so we have a mobile laboratory here to monitor the quality of the air," Blanchette said in an interview.

"We also have a spill on the lake and the river that is concerning us. We have advised the local municipalities downstream to be careful if they take their water from the Chaudiere River."

Officials were still worried about air quality Saturday night as smoke continued to billow into the sky.

A spokeswoman for Stephen Harper said the prime minister planned to visit the community on Sunday.

Harper expressed his sympathy Saturday during a news conference in Calgary.

"What has happened is shocking and truly devastating," Harper said. "My thoughts and prayers and those of all Canadians are with the people of Lac-Megantic as they deal with this disaster in their community."

"There will of course be a full investigation into what has caused today's horrendous events but for now our thoughts and our efforts remain focused on those personally effected by this tragedy," he added.

Liberal Leader Justin Trudeau also commented on the events.

"My thoughts are with all the families who have had to be evacuated, and especially with all those who are searching for their loved ones," said Trudeau.

The explosions attracted worldwide media coverage, with the story trending as the most sought after international story on the BBC's website as well as featuring on other sites including Le Monde's.

Back in Lac-Megantic, Theberge, whose arm was wrapped tight in a long white bandage, thought about his escape as he sat outside a high-school-turned-shelter for evacuees.

"All of this happened in matter of 10-15 seconds," Theberge said of the time that elapsed between the sound of the train bearing down on the town and the massive explosion that transformed it.

"I'm lucky."