One person is dead after a two-vehicle collision on Highway 401 early Sunday morning.

It happened in the westbound lanes just before Highway 427 at around 6:50 a.m.

According to OPP Sgt. Dave Woodford, a BMW lost control, struck a guard rail, crossed the median and hit a tractor-trailer head-on before bursting into flames.

The cause of the accident is still under investigation.

"We will look at speed, we will look at mechanical and we will look at the alcohol factor if any to determine why that BMW initially lost control and hit that barrier," Woodford told CP24.

All westbound lanes on Highway 401 were closed at Martin Grove Road as police investigated, but two lanes reopened at 12 p.m. and the others opened a few hours later.

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