Commuters using Highway 401 in Toronto dealt with major delays due to lane closures caused by a fatal truck fire just before the morning rush hour at Avenue Road, but all lanes have been cleared in time for the evening commute.

One man died at the scene at Avenue Road this morning, according to Toronto paramedics. 

Const. Lauren Ball, OPP spokesperson, said that the flatbed truck hit the side of a second truck that had pulled over into the right-hand shoulder of the express lane.

The flatbed lost control, hitting the centre median and catching fire. The OPP said it's too early yet to know what caused the flatbed to veer onto the shoulder.

401 traffic gridlock0:36

Police are appealing for witnesses to help determine the cause of the crash.

Capt. David Eckerman, spokesperson for Toronto Fire Services, said the fire department got several calls about the fire at about 5:15 a.m.

Callers reported hearing an explosion and seeing fire across all lanes and a fireball.

When fire crews arrived on the scene, the transport trailer was fully engulfed in flames. It appeared close to the barrier of Highway 401's eastbound collector lanes east of Bathurst Street. 

Fatal 401 truck fire0:48

Thousands of cars were backed up on the highway. Traffic was backed up all the way to Dixon Road, including onto Highway 409. 

At Keele Street and Highway 401, collector lanes were moving slowly, but the express lanes were completely at a standstill.

At peak congestion Monday morning, people had stepped out of their cars and were talking to each on the highway. 

While collector lanes had cleared by the lunch hour, express lanes remained closed for a portion of the afternoon as crews checked the condition of a light post hit by the flatbed.

Fatal truck fire on Highway 401

Toronto firefighters spray water on a truck fire on Highway 401. (Tony Smyth/CBC)

"We were delayed by extremely heavy traffic in our approach, but once we did finally start to get water onto the fire from two of our trucks, of which we sent five, we got the fire under control in about five minutes," he said.

Fire crews ran hoses from Wilson Avenue down sidestreets to Highway 401.

The OPP said some damage to the road underneath the flatbed is likely as asphalt would have burned in the inferno.

Absorbent material will be placed on the highway. One truck lost part of its load of paint, which the OPP said contributed to long delays.