Eight more bodies have been found in Lac-Mégantic, Que., bringing the official body count up to 13 people after a runaway train carrying crude oil set off a series of explosions and flattened the town's busy downtown.

Police said some 50 people are missing — a figure that includes the 13 unidentified bodies that have been recovered since the train derailed at about 1 a.m. ET Saturday.

Police are asking family members to provide toothbrushes, combs, or other items that might provide DNA from their missing relatives to help investigators identify the bodies.

About 2,000 of the town's 6,000 residents were forced to leave their homes on Saturday, but 1,500 of those evacuees may be able to return home as soon as Tuesday.

While some residents prepare to move home, the community has a long road ahead as it faces rebuilding the downtown core that was levelled in the series of blasts.

Railway official denies negligence

Before the train carrying crude oil rolled into town after midnight, it was parked uphill in Nantes — about 12 kilometres from Lac-Mégantic.

The president of the railway's parent company, Rail World Inc., said the train was properly secured before the engineer left for the night.

Witnesses in Nantes said that they had seen sparks and a cloud of diesel smoke as the train came to a stop a few hours before the derailment.

Lac-Mégantic's fire chief said that Nantes firefighters had answered a call about a fire aboard the locomotive less than three hours before the train rumbled into Lac-Mégantic.

'Nothing the firefighters did could have put the train in jeopardy.'—Patrick Lambert, Nantes fire chief

Edward Burkhardt, the chairman of the board of Rail World Inc., said that by shutting off the locomotive in order to deal with the fire, the firefighters could have unknowingly shut off the train's air brakes.

"As the air pressure depletes, [the brakes] will become ineffective," he said.

However, firefighters in Nantes said when they left the train it was in the care of a track maintenance employee.

Burkhardt said the track maintenance employee might not have known how to re-secure the train's brakes, but he said local firefighters should have done more, suggesting they could have called the engineer who was asleep just across the street.

Nantes fire chief, Patrick Lambert, said his colleagues did their job.

"Nothing the firefighters did could have put the train in jeopardy," Lambert said. "They had two people come meet us … They said everything was out, the fire was out and everything was stabilized and that we could leave."

Ultimately, Burkhardt downplayed his company's responsibility.

"Is any of this huge negligence? No you can't point to that," he said.

A tragedy that was 'bound to happen'

The leader of Quebec's Coalition Avenir Québec, François Legault, said he expects there will be significant changes to railway regulations after the investigation has been completed.

"It's not acceptable that we see trains with oil so close to houses," he said on Monday.

"Many people here say it’s as if it were a tragedy that was bound to happen, to have railway cars coming so close to people."

Questions are also being raised about whether Canada's railways should have heightened surveillance and stricter regulations.

On Monday morning, a train was found parked on the tracks near the town of Lac-Mégantic, sitting with its doors unlocked.

CBC's Daniel Halton said the train "had been left alone for two days, its door unlocked, allowing anyone access to the control panel."

Over the weekend, Prime Minister Stephen Harper promised to draw lessons from the federal Transportation Safety Board's investigation in order to prevent a repeat of such a tragedy.

Liberal Leader Justin Trudeau visited the scene on Monday, and said he was "blown away by the terrible destruction ... but also by the strength and the courage of the people who've come from across the country to help out."

Environmental concerns

The area surrounding the derailed tanker cars has remained largely off limits to anyone other than fire crews. While the flames have been extinguished since Sunday, firefighters are keeping a close watch on certain "hot zones" that still pose a risk.

Public health and environment officials say they're still assessing the impact of the massive oil leak and fire on the area inside and outside of the security perimeter.

Quebec Environment Minister Yves-François Blanchet told CBC’s Quebec AM that he flew over the Chaudière River Sunday to see the extent of the damaged caused by the oil spilled from the derailed tankers.

"What we have is a small, very fine, very thin layer of oil which, however, covers almost entirely the river for something like 100 kilometres from Lac-Mégantic to St-Georges-de-Beauce," he said.

"This is contained at St-Georges-de-Beauce for the time being, most of it, or almost entirely, and we are very confident we will be in a position to be able to pump most of it out of the river. However, there will be some impact."

He said an estimated 100,000 litres of oil spilled into the river.

Officials at the scene said contamination to the soil appears to only affect the surface, but further testing will be done by the environment ministry. They stressed that rehabilitation work is the immediate priority.

Medical services located inside the safety zone will be relocated until they are able to return to their spaces, officials said.

Locomotive was inspected 1 day before derailment

Transport Minister Denis Lebel said on Monday that the cause of the derailment remains unclear.

"But we do know Transport Canada inspector inspected the locomotive involved in this event just the day before it happened, on July 5, and found no deficiencies," Lebel said.

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A group sits near Polyvalente Montignac, the school sheltering the people who were forced to leave their houses after the train explosion that killed at least 13 people. (Mathieu Belanger/Reuters)

According to Lebel, the Conservative government has taken "concrete action" to improve rail safety over the years.

Federal TSB officials said they planned to interview all possible participants as part of what they called a "360-degree," top-to-bottom, investigation.

They have retrieved two so-called "black boxes" from the train, which will provide investigators with important data about the train's speed and brake pressure leading up to the derailment.

With files from The Canadian Press