The two employees of B.E.M. Fireworks — a company that designs and produces fireworks displays — were killed in the explosion, which happened just before 9 a.m. today at B.E.M.'s warehouse, located just off Highway 20, about 50 kilometres from Montreal.
Police have not identified the dead, however, they have confirmed they were both women and mothers of young families.
Evacuees allowed home
Public health authorities have now lifted a one-kilometre evacuation zone around the smoking remains of the plant. There had been a concern earlier in the day that trace amounts of heavy metals and other particles could irritate people's eyes and respiratory passageways.
About 40 homes and a campground were evacuated shortly after the explosion.
The explosion happened at a warehouse on the B.E.M. property that stored industrial-strength fireworks, flattening the building.
"That's why there was so much heat and flames — from the fireworks exploding," said Coteau-du-Lac fire Chief Stéphane Massicotte.
For hours after the first blast, fireworks kept on exploding, igniting a secondary fire and sending heavy smoke into the air, as well as a sulphurous odour that could be detected as far away as southwest Montreal.
"We got really, really, really scared," Ginette Liboiron, who runs a convenience store across the highway overpass, told The Canadian Press. "I thought my store was falling to the ground. It shook like you can't imagine.… We all went outside to see and saw the big, incredible smoke.
"Then the fireworks went off."
Felicien Chouinard was making breakfast in his trailer when he felt what he described as "an earthquake."
"It was hell — the whole trailer shook," he said. "When we went outside we saw an immense cloud of smoke and then there were more explosions."
Water trucked in, with no hydrants nearby
The fire was brought under control by early afternoon, but for close to six hours, 150 firefighters from 14 nearby municipalities helped Coteau-du-Lac's small fire department — mostly carting water in with their fire trucks, as there were no fire hydrants located near the 40-year-old factory.
"You can't talk about sprinkler systems," said Massicotte, in response to a reporter's question. "There is no municipal water system. As far as safety goes, the building was inspected regularly. The factory's management was always co-operative."
"I have no reason to believe there was any negligence."
The cause, believed to be accidental, is now under police investigation.
Highway 20 was closed in both directions at the scene, causing a traffic mess in the area, CBC's Sean Henry reported. Cars were rerouted to small streets, backing up traffic for a long stretch.
The highway reopened at around 1 p.m. ET.
Via Rail tweeted that it had reopened the tracks after confirming that one train travelling between Quebec City and Ottawa had earlier been held up at Les Cèdres because of the explosion.
According to its website, B.E.M. has been designing and manufacturing pyrotechnics and fireworks for 25 years.
Coteau-du-lac Mayor Robert Sauvé said the owner of the business is a resident of the town and the company employs around 20 people.
"This is a very sad day for Coteau-du-lac," he said. "This was a very respectable business in our view and, what happened this morning was an accident. Obviously, we'll see as time goes by with the results of the investigation exactly what happened — what caused the explosion."
The company occupies a sprawling property near Highway 20 that included a store and warehouse.
CBC reporter Steve Rukavina reports from Coteau-du-Lac as firefighters mop up after the deadly explosion.