The official death toll has grown to five in Lac-Mégantic, Que., after a derailed train carrying crude oil exploded in the town's core, levelling buildings and forcing as many as 2,000 people from their homes.

Quebec provincial police said two more bodies were discovered Sunday morning, in addition to the three that were found the night before in the hardest-hit area in the centre of town.

A spokeswoman for the coroner's office said the bodies were found with advanced burns.

Police say about 40 people have been reported missing by immediate family members in the town of about 6,000 people, located roughly 250 kilometres east of Montreal.

The number of missing people continues to fluctuate, as some of those reported missing are reunited with their families.

Police say will continue to search the area for victims and officials fear the death toll will rise in the days to come.

'This is an unbelievable disaster.' —Prime Minister Stephen Harper

"We know there will be other deaths," said Sûreté du Québec Lt. Michel Brunet.

The bodies have been transported to Montreal for autopsy. Police would not confirm any details about the deceased or where exactly they were located, saying families are still being contacted.

Prime Minister Stephen Harper visited the site of the blasts on Sunday, describing it as a "war zone."

"There are going to be difficult times to come," he said. "I’m here to say we understand your pain, and we will stand by your side."

Harper said all levels of government are cooperating to ensure members of the community are supported.

“This is an unbelievable disaster," he said. "Obviously, there will be investigations to determine that it doesn’t happen again.”

By Sunday afternoon, officials had reduced the security perimeter and allowed some residents back into their houses. But the return home was difficult for many who were still missing family members.

Fire officials said there are still hot spots where firefighters continue to work, but the flames were extinguished for the most part by Sunday afternoon.

Police have labelled the area of the explosion as a crime scene.

"In a fire like this one, where there is major destruction and multiple deaths, the Sûreté du Québec must investigate to see if there are any criminal elements ... so it becomes a crime scene," said Lt. Brunet.

Runaway train was parked on hill

A statement released Sunday by Montreal, Maine and Atlantic Railway, said it is possible the train's air brakes released after it was parked for the night, allowing it to roll out of control until it derailed at the centre of Lac-Mégantic.

The train was in Nantes on Saturday night, about eight kilometres from the town of Lac-Mégantic. According to a company statement, the train rolled away after the engineer had left and gone to a nearby hotel for the evening.

On Sunday, authorities were able to gain access to the black box, known as the locomotive event recorder, at the site of the explosion. Once analyzed, it will help investigators determine the circumstances surrounding the derailment.

Mass evacuations

Many residents who have been forced from their homes are gathering at an evacuation centre set up by the Red Cross at a local school.

Nearly 1,000 people were forced to leave early Saturday morning and another 1,000 were under evacuation orders later that day because of air quality concerns.

"The majority of people have found a place with family and friends," said Myriam Marotte of the Red Cross.

"It's a small community and what we see is a lot of solidarity. People are helping each other."

On Saturday night, 163 people stayed in that emergency shelter. Another 550 registered with the Red Cross so they could be accounted for.

In addition to food and shelter, psychological services are being provided to those who need it in the close-knit community.

"It's difficult for people who still are looking for loved ones," said Marotte. "It's also difficult for people who don't know what is going to happen in the next couple of hours and couple of days. Some people have lost everything."

Dozens still unaccounted for

CBC's Stephen Puddicombe spoke to one woman at that centre who said she hasn't heard from her 17-year-old daughter since the explosion. The girl was in the centre of town, the epicentre of the devastation, when the train derailed at about 1 a.m. Saturday.

An unofficial list of missing persons has been set up online for those still looking for loved ones and friends. Dozens of people once on that list have since been located, according to confirmations submitted online. The list is still more than 200 names long.

Boil-water advisory

The mayor of Lac-Mégantic, Colette Roy-Laroche, said the town will be under a boil-water advisory as a precautionary measure until further notice.

The town's drinking water was in short supply because of a leak inside the security perimeter on Saturday evening.

A city employee was able to stop the leak, and the city said the water reservoirs are filling up. Roy-Laroche said residents should boil their water for at least five minutes before drinking.

“We are currently analyzing water samples and if the situation is deemed normal then we will let our citizens know … that we are lifting the advisory."

Witnesses described the scene as devastating.

"It's a mess," said Lac-Mégantic fire chief Denis Lauzon, who added that many historic buildings and the town's library and archives were destroyed.

Yves Faucher, who lives in the centre of town, was among the first wave of evacuees.

"I saw though my windows, it became bright like the sun. I thought it was an explosion," he said.

He said he tried to warn people to flee rather than stand around and watch the fire, fearing another explosion.

Witnesses reported hearing between five or six blasts as other tankers filled with oil burst.

with files from Canadian Press