MONTREAL — Quebec provincial police added a fourth person to the list of victims as they worked to establish what triggered a deadly highway pileup north of Montreal on Monday afternoon.
The investigation of the crash that also left 15 people injured — including three severely hurt — was ongoing on Tuesday as Highway 440, in Laval, Que., reopened to traffic at about 5 a.m.
It happened on a busy stretch of highway that runs east-west through Laval, the province's third largest city.
Two tractor trailers and several cars were involved in collisions at the exit leading to the interchange for Highway 15, which runs north to the Laurentians and south to Montreal.
Police say at least one of the trucks hit a passenger vehicle, setting off a chain reaction. A thick cloud of black smoke could be seen billowing in the air.
Provincial police asked anyone who may have witnessed the moments preceding the crash at around 3:30 p.m. Monday to come forward.
Police said all four victims died at the scene, but identifying them could take time.
"The victims aren't easily identifiable," said Sgt. Daniel Thibodeau. "There's also the vehicle identification numbers, but some of the burned vehicles are too damaged to make out those identification numbers."
Investigators also hope to speak to survivors of the incident once their health allows it.
Quebec Transport Minister Francois Bonnardel promised immediate action Tuesday, even though little is known about the cause of the crash.
Bonnardel said that since 2013, there have been about 10 accidents at the interchange, including one other fatality. The transport minister said that in the short term, safety in the area will be improved by extending the portion that forbids drivers from merging at the last minute to exit the highway and access the service road.
"We will do it to change the behaviour of drivers, to stop them from entering at the last minute," Bonnardel said, noting that roughly 300,000 vehicles use Highways 440 and 15 daily.
In the longer term, Bonnardel said an assessment will be done across the province to identify spots where similar measures are needed.
The minister noted that a lot of interchanges in Quebec — many of which are just as heavily travelled — have configurations that are 40 to 50 years old.
Bonnardel offered his condolences and praised the work of first responders who helped at the scene.
Laval police reported Tuesday that 10 of its officers were taken to hospital to be treated for exposure to the intense smoke. All were released.
Finance Minister Eric Girard, who is also the minister responsible for the Laval region, and Laval Mayor Marc Demers toured the area alongside Bonnardel.
Quebec Premier Francois Legault also extended his condolences and urged anyone needing psychological help to get it.
"All my thoughts are with the relatives of the victims involved in the terrible accident yesterday on Highway 440," Legault wrote on Twitter. "I want to thank the first responders and emergency services."
Sidhartha Banerjee, The Canadian Press