A hit-and-run is what caused a serious crash in Bradford Sunday morning that sent two people to hospital and closed Highway 400 for hours, police say.

Ontario Provincial police said a vehicle, possibly a tractor trailer, clipped a vintage Triumph TR3A and sent it spinning into a guardrail shortly after 9 a.m.

The Triumph, which was travelling north, just south of the Highway 89 exit, struck a cargo van after it was hit. The van rolled from the impact but landed back on its tires.

The van's two occupants walked away from the scene relatively unscathed, but the two people inside the Triumph were seriously hurt. The driver of the car was airlifted to Sunnybrook Health Sciences Centre in Toronto with life-threatening injuries.

The northbound lanes of the highway between Highways 88 and 89 reopened at about 1:30 p.m.

The Ontario Provincial Police at the scene spent most of the morning trying to reconstruct the events leading to the accident.

OPP Sgt. Steve Cartwright told CTV.ca a tractor trailer may have not noticed it was involved in an accident before continuing on its way. Police are trying to find the truck.

Authorities are asking for any witnesses to call investigators at 905-841-5777.

Meanwhile in Milton, a 17-year-old boy was killed in an early morning rollover.

Police say they suspect speeding and alcohol were factors in the crash that sent a car slamming into a guard rail on Tremaine Road just south of Britannia at around 5 a.m.

The car flipped over several times. An 18-year-old girl was rushed to hospital where doctors amputated her foot. The driver of the car received life-threatening head injuries and another teen suffered serious leg wounds.