Police have begun a criminal investigation into the train derailment explosion that took five lives in Lac-Mégantic, Quebec on Sunday. Forty people are still unaccounted for.

The driverless train exploded in the small town 150 miles from Montreal, forcing 1000 people to evacuate after extensive fires overtook the town. Prime Minister Stephen Harper visited the community on Sunday and called it a “war zone.”

The burned out site is currently cordoned off as a "crime scene," and the conditions of the train explosion seem to indicate foul play.

The chairman of the Montral, Maine & Atlantic Railway, Ed Burkhardt, reported on Sunday night that the train's only engineer shut down four of the five locomotive units on the train before heading to Lac-Mégantic. This is standard procedure. The engineer then went to sleep. Burkhardt said that the next engineer was due to arrive at dawn.

Burkhardt reports that someone managed to shut down the fifth locomotive unit. This final unit maintains brake pressure needed to keep the train steady. Burkhardt says the two ways to shut down this unit—an emergency lever outside of the train as well as a combination of levers and buttons inside the unlocked cabin—were both employed.

"We've had a very good safety record for these 10 years," he told USA Today, "Well, I think we've blown it here." After this explosion, Burkhardt said they would "consider" changes to their safety policies.

The "black box" has been recovered and will be examined for evidence.

More than one hundred firefighters are searching for the missing parties. Sargeant Benoit Richard reported that "There is still a big part of the scene that is too dangerous to examine." A secondary school transformed into a emergency shelter where town residents are seeking information about their relatives.

[image via Getty]