Lac-Megantic, Quebec (CNN) -- Canadian authorities have found evidence that a criminal act may have led to a train crash in Lac-Megantic, Quebec, that killed at least 15 people, provincial police Capt. Michel Forget said Tuesday.
There have been many questions about the crash and explosion that wiped out a swath of the town 130 miles east of Montreal. As of Tuesday evening, 35 people were still missing, Forget said.
Authorities offered no further details about the case but said it was not caused by terrorism.
"I will not speculate on the elements that we have recovered," Forget told reporters.
Investigators had earlier said that they are trying to figure out whether the train's brakes were disabled before it barreled at a dangerous speed into the Quebec town, derailed and burst into a deadly inferno.
Firefighters in the nearby town of Nantes put out a separate blaze on the train shortly before it crashed into Lac-Megantic early Saturday. Ed Burkhardt, chief executive officer and president of Rail World, the parent company of the Montreal, Maine & Atlantic Railway, has told media outlets there's evidence the engine powering the brakes was shut down at some point.
Pressed to elaborate by CTV, Burkhardt wrote Tuesday in an e-mail exchange, "We are now aware the firefighters shut down the locomotive. By the time (Montreal, Maine & Atlantic) people found out, it was too late."
In earlier comments to the Montreal Gazette, he said the matter needs further investigation, and his company has begun an internal inquiry.
"There are a number of missing pieces here," Burkhardt told the paper, saying he didn't suspect "the event was malicious or an act of terrorism."
The company did not immediately return phone calls from CNN about the report.
Asked during an earlier news conference whether authorities suspected sabotage, Ed Belkaloul, manager of rail operations for Canada's Transportation Safety Board's eastern region, said there was no evidence to that effect.
The train began rolling -- unbeknownst to dispatchers and rail traffic controllers -- about an hour after the fire in Nantes was reported. It picked up speed because the track between Nantes and Lac-Megantic lies on a 1.2% downward slope, which Belkaloul said is relatively steep.
"On the principal lines, as soon as there is an uncontrolled movement, the controllers of rail traffic can see that there is an uncontrolled movement," Belkaloul said. But on smaller lines like the one between Nantes and Lac-Megantic, "there is no way for the dispatcher or the controller to realize that there is an uncontrolled movement."
Seventy-two tanker cars carrying crude oil jumped the track early Saturday, setting off a huge fireball.
Officials in Lac-Megantic say some victims were likely vaporized by the intense blaze, which burned for 36 hours after the crash.
The fire is under control, authorities said Tuesday morning. Of the roughly 2,000 residents evacuated, about 1,200 will be permitted to return home immediately. Another 800 cannot go back yet, the officials said.
Notices were placed on doors instructing residents how to clean and air out their homes. Officials suggested throwing out any food and boiling all water because the city's water treatment plant is not operational.
Firefighters are now using infrared detectors to find any remaining hot spots in the wreckage. They've stopped hosing down the area because it was inhibiting the investigation, officials said.
Rolling oil bomb?
The train had already been on fire hours before the Saturday accident, Canadian broadcaster CBC reported, sourcing fire officials. Firefighters in the town of Nantes, seven miles northwest of Lac-Megantic, extinguished a small blaze on the freight train.
When they left, the train was still parked where it was supposed to stay for the night, the Montreal, Maine & Atlantic Railway said.
Earlier, the company said air brakes holding the train in place failed, allowing it to barrel downhill into Lac-Megantic. It was not clear if Rail World executive Burkhardt was suggesting to CTV that firefighters were responsible for disabling the brakes, but he told Reuters earlier that the brakes were disabled when firefighters shut down the engine powering them.
Investigators plan to check the brakes once the crumpled, burned tankers are accessible.
The train rolled into town much faster than a train under an engineer's control would have.
"Usually they're traveling between 5 and 10 miles an hour," said Quebec police officer Benoit Richard. "On that night, this train was going at least between 30 and 40 miles an hour."
Sonia Pepin recalls hearing the train like never before. The tracks are a few feet from her home, and her whole house shook, she said.
Investigators with the Transportation Safety Board of Canada found the locomotive event recorder, which they can analyze for information on throttle position and speed, among other data.
Oil transport safe?
Petroleum products have increasingly been transported via rail in the past five years, according to the railroad industry, and Canada has had multiple issues with derailments in recent months.
Last month, four Canadian Pacific rail cars carrying flammable petrochemicals used to dilute oil derailed on a flood-damaged bridge spanning Calgary's Bow River, according to the Calgary Herald.
In another incident involving Canadian Pacific, five tankers containing oil derailed in rural Saskatchewan in May, spilling 575 barrels of crude, the Toronto Sun reported.
A month earlier, 22 Canadian Pacific rail cars jumped the tracks near White River, Ontario. Two of the cars leaked about 400 barrels -- almost 17,000 gallons -- of oil, The Globe and Mail in Toronto reported.
Canadian Pacific was also involved in a stateside spill in March. Fourteen cars on a mile-long, 94-car train derailed in western Minnesota, about 150 miles northwest of Minneapolis, spilling about 30,000 gallons of crude, Reuters reported.
A rail car can carry roughly 700 barrels of oil, with 42 gallons per barrel.
Popular Quebec performer missing
The runaway train rumbled toward Lac-Megantic while patrons at the Musi-Cafe were enjoying a summer night of live music. Some were sitting on the pub's front porch.
The Musi-Cafe is no longer standing, one of an estimated 40 buildings leveled in the crash and explosions. Some of its patrons have been counted among the 13 confirmed dead.
"We know that there will be many more," said police Lt. Michel Brunet.
Authorities believe some of those still missing were in the pub at the time of the accident. Quebecois musician Guy Bolduc had been performing there.
The pub's Facebook page is filling up with messages of condolence, as has a page created for the victims of the disaster. Bolduc's fans are searching for him on social media.
"All of his fans, all over Quebec, but also his fellow singers (of whom I am one) hope to see him again alive!!! Come on my GuyBol, come out of your hiding place," one member wrote.
"Hot zones" lingering more than two days after the train derailment hampered authorities' efforts to search for missing people.
Forensic specialists have asked victims' families for hair samples, clothing, anything to help identify their loved ones.
In a town of just 6,000 residents, most everyone is affected by the deaths and destruction.
Prime Minister Stephen Harper has described the scene as a "war zone."
CNN's Holly Yan, Umaro Djau, Jonathan Mann, Pierre Meilhan and Deanna Hackney contributed to this report.