Two men have died following a multi-vehicle crash on Highway 401 in Ajax.

The collision occurred in the eastbound lanes of the highway near Harwood Avenue, at approximately 6:20 a.m. on Wednesday.

Police have not said what caused the crash, but said that it was dark and foggy in the area at the time. A fog advisory issued by Environment Canada on Wednesday warned visibility was reduced to 250 metres in some parts of the Toronto area.

A witness told reporters on scene that a chain reaction crash occurred when a transport truck collided with vehicles moving slowly through the fog. The witness said a total of eight vehicles were involved.

“When I got hit, there was a loud explosion of metal crunching together. I didn’t know what was happening,” said Volmar Mills, one of the motorists who was caught in the pileup. “I was pushed forward into another car in front of me.”

Two of the vehicles were transport trucks, which sandwiched an SUV between them when they collided.

The 63-year-old driver of the SUV was trapped inside the vehicle at the time. Crews worked for nearly two hours to free the driver, but he or she succumbed to injuries at the scene.

“I can’t say enough about the firefighters that were on the scene -- the effort that they put forward here,” said Ajax Fire platoon chief Ron Evans.

Officials said another man was injured in the collision was being treated for life-threatening injuries, but the 57-year-old succumbed to his injuries at approximately 4 p.m. on Wednesday.

No one else was seriously injured in the crash.

All eastbound lanes were closed to traffic as crews worked on the scene. The lanes have since reopened.

With a report from Zuraidah Alman