Ontario Provincial Police Sgt. Kristine Rae says the collision between a Megabus and a tractor-trailer Tuesday afternoon on Highway 401 remains under investigation and police "haven't made any determination on what caused the crash yet."
Jeff Boyle, a spokesman with Caravan Group of Companies that owns the truck involved in the collision with a double-decker bus, says the driver of the truck is shaken up, but otherwise healthy.
Boyle says the truck was hit from behind by the bus, clipping the back corner and moving along on the right side of the truck before taking out the passenger-side mirror.
The bus, which was carrying about 45 passengers between Montreal and Toronto, then continued into the ditch near Lancaster, Ont., before coming to a rest.
Megabus.com North America said it had no comment on the trucking company's allegation that the bus struck the tractor-trailer from behind.
"We certainly don't want to comment on something that's an ongoing investigation," said spokesman Sean Hughes.
The company has said safety is its top priority and is co-operating with investigators.
Police earlier confirmed that the front of the bus had been damaged.
A woman remains in serious condition and three others also remain in hospital, police said Wednesday.
Passengers on the bus described what felt like the bus braking hard or the feeling of a blown tire. Several passengers said people were thrown from their seats, as the bus sped into a ditch on the side of Highway 401 before coming to a crashing halt among the trees lining the westbound lanes.
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