Commuters were hit by massive delays on Highway 401 in North York after a fatal collision between two trucks early Monday morning.

A large stretch of the highway, including the collector lanes, was shutdown by police, but all lanes reopened almost 11 hours later at around 4:15 p.m.

Toronto Fire Services say that callers reported an “explosion” and fire across all lanes at 5:15 a.m. The collision occurred on the eastbound express approaching Yonge St., according to the OPP.

Investigators told media on scene that a truck carrying paint was at a stop on Hwy. 401, east of Allen Rd., when a flatbed truck carrying skids of chalk deviated onto the eastbound lane and collided with the truck.

When Toronto fire arrived on scene after being delayed by heavy traffic, they found the flatbed was “fully engulfed” in flames.

Paramedics confirmed that the driver of one of the trucks was killed in the collision. Although Toronto fire is not sure exactly how many vehicles were involved, paramedics also treated a male driver of another vehicle for a minor shoulder injury.

Police say they are investigating how the flatbed truck drifted into the second truck.

Toronto fire said they were able to have the blaze under control in around five minutes.

But the cleanup took a lot longer than that, Toronto fire Capt. David Eckerman says.

One of the trucks had 50-gallon drums of paint and paint thinners on a flatbed, he said, and the paint spread across the lanes in the accident.