Twenty-four bodies have been recovered as of Thursday out of a total of 50 people missing since the explosion. The number of victims located is expected to rise as crews on the disaster site continue their work.

One of the victims has been positively identified as Éliane Parenteau, 93.

Evacuations originally removed 2,000 people from the area. Thursday afternoon, 600 evacuees from the Cousineau district were allowed to return home. About 1,200 town residents were allowed to return as of Tuesday morning. Roughly 200 are still barred from their homes within the area still cordoned off.

Lac-Mégantic Mayor Colette Laroche-Roy declared a state of emergency for the foreseeable future.

Église Sainte-Agnès will open its doors day and night starting Friday so the community can gather and mourn.

Roughly 40 buildings, in the town’s centre, were completely destroyed.

The sewer system in the downtown core has been badly cracked and will have to be replaced.

Officials estimate some 100,000 litres of oil leaked into the ground and nearby waterways after the tragedy, but the cleanup is going well and no public health threat is foreseen in communities along the Chaudière River.

Nonetheless, Urgence Québec recommended that people halt swimming and water sports in the Chaudière.

The train was being operated by Montreal, Maine and Atlantic Railway (MMA). It had been using five locomotives to pull 72 tankers, each filled with tens of thousands of litres of light crude oil from fracking operations in North Dakota to an Irving Oil refinery in New Brunswick.

The Transportation Safety Board of Canada (TSB) has 14 investigators on scene and more support at its headquarters and laboratory in Gatineau.

The TSB is still in the first phase of a three-part investigation.

The train stopped at approximately 11 p.m. Friday in nearby Nantes.

Firefighters from Nantes were called at 11:32 p.m. to extinguish a fire in one of its five locomotives. The rail-traffic controller, off site, was notified at 11:50 p.m.

About midnight, that locomotive’s engine was shut down and the fire extinguished.

Firefighters were joined by an employee from the MMA.

The last firefighter on scene left at 12:13 a.m. Saturday.

After the last MMA employee subsequently left, the train was left unattended.

It started to roll — on its own — at 12:56 a.m.

The runaway train descended a 1.2% grade heading downhill toward Lac-Mégantic, picking up speed as it went.

The train crashed inside the town’s core at 1:14 a.m. Many tanker cars jumped the tracks, as they reached a curve in the tracks at an excessive speed.

The five locomotives detached from the rest of the train.

Investigators have been able to determine the position of the controls in the locomotive at the time of the crash, from the locomotive event recorder. Data from the sense and braking unit at the back of the runaway train has also been recovered. Those devices are commonly referred to as black boxes.

There were no signals or track circuits on that track — so the rail traffic controller would have no indication of a runaway train.What is unknown

The investigation:

What caused the train to break away? It is still undetermined what precisely caused the tanker cars to move on their own, gain momentum along the downhill grade, derail and explode.

MMA officials confirmed to The Gazette that hand brakes were engaged on all five of the train’s locomotives. But it’s unclear how many of the 72 tanker cars had their hand brakes activated.

Edward Burkhardt, the railway company’s chairman, said Wednesday afternoon that train engineer Tom Harding told the company he had activated 11 handbrakes before leaving the train unattended late Friday, prior to the locomotive fire. Burkhardt also said that “our general feeling now is that that’s not true. Initially, we took him at his word.”

It’s also unclear whether the securement test was performed, where a train to be left unattended is nudged in order to mimic a strong gust of wind or other external force — to ascertain that it won’t move.

Patrick Lambert, the fire chief at Nantes where the train had been stopped, said that after his fire crew had extinguished the locomotive fire, one of them had shut down the locomotive in question. At least one MMA employee remained on the scene at 12:13 a.m., when the last of the firefighters left. “We don’t touch the brakes,” Lambert specified.

The TSB said Tuesday that “we are still working on ... a number of operational issues.”

These include: “the operation of the train, and the requirements and company policies regarding securement of trains,” including “locked doors, adequate brakes;” and “the packaging of dangerous goods, and their performance,” such as how the Class 111 tanker cars perform in derailments.

The probe is in the first of three phases, the field phase.

Thursday, Transport Canada confirmed by email that the use of a single crew member on the train is part of the investigation.

In Canada, for a railway to rely on a solo crew member to operate a train the company must first carry out a “review of their Safety Management Systems to verify they have the appropriate technology in place to support single person operations,” Maryse Durette, senior media relations adviser with Transport Canada, added.

“Regulatory action under the Rail Safety Act can be used if the parameters for single person train operation (SPTO) are not met or if Transport Canada determines that there is a risk to safe railway operations,” the email said: “These matters will all be a part of the TSB investigation.”

The second phase of the TSB investigation will include examination and analysis. “When safety deficiencies are suspected or confirmed, the TSB advises the appropriate authority without waiting until publication of the final report,” the TSB had said Tuesday.

The third step will be the report phase, during which “a confidential draft report is approved” by the TSB “and sent to persons and corporations who are directly concerned by the report. They then have the opportunity to dispute or correct information they believe to be incorrect.” Afterward, the TSB “considers all representations before approving the final report, which is subsequently released to the public.”