Two adults and a 12-year-old boy are dead and 16 others are injured after a transport truck failed to slow down for construction along Highway 401 near Ajax on Friday night and crashed into a number of slow-moving vehicles.

According to Ontario Province Police, the fully-loaded truck was travelling westbound at around 10:30 p.m. when it collided with traffic near Salem Road, causing a chain-reaction collision that involved four transport trucks and 16 other vehicles.

The two adults that were killed in the crash were travelling in one vehicle while the 12-year-old victim was in another vehicle. Police say that the family of the 12-year-old victim were also injured in the crash and are “fighting for their lives” in hospital.

Of the 16 injured parties, OPP say five are in critical condition and the others are in serious but non-life threatening condition.

Police are continuing to probe the circumstances surrounding the accident, though speed has already been confirmed as a factor. According to Sgt. Kerry Schmidt, police will also look into whether impairment or fatigue played a role in the crash and will conduct inspections of all of the vehicles involved to determine whether or not there may have been a mechanical factor at play.

It is not immediately clear whether or not the transport truck driver made an attempt to stop prior to the collision.

“All the witnesses we have spoken to said this vehicle was travelling westbound and did not slow down as traffic was slowing down. As you can imagine, when that energy and that mass of a vehicle crashes into cars that are essentially stopped or moving very slowly the damage is horrific,” Schmidt told CP24 at the scene Saturday morning. “The cars were just ripped open like tin cans almost. It was incredible the amount of damage that was sustained.”

Signage was posted warning of construction

Schmidt said the stretch of Highway 401 where the accident occurred usually has three lanes of traffic but was down to two at the time of the crash due to the construction.

There were signs in the area indicating that there was construction ahead, Schmidt said, but the driver of the transport truck, which was loaded down with steel, did not slow down in anticipation.

The resulting crash made a massive noise and shook nearby homes, according to a number of residents

“I was sitting watching TV and all of a sudden I heard crash, bang boom and I fell out of bed. It was the worst accident I have ever seen,” one woman told CTV News.

“It was rumbling. You could feel it on my sofa and it went on for 15 or 20 seconds, or at least it felt like that,” another man who lived nearby told the network.

Schmidt said that many vehicles were “twisted and damage beyond recognition” following the crash.

As a result a number of people were briefly trapped in their vehicles, several of which were wedged under transport trucks.

Those people were then extricated after about an hour.

It took longer, however, to access the bodies of those killed in the crash.

“It took some time to get the people out of these vehicles. Where the deceased were, they were basically underneath the transport truck as it drove up and on top of the car, so they actually had to pull one of the transport trucks apart to get access to the vehicle,” Schmidt told CP24.

The highway was closed in both directions between Brock and Salem roads for several hours for a police investigation.

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