PRESCOTT, Ont. – Police say two people were seriously injured in a series of collisions on Highway 401 between Prescott and Highway 416 in eastern Ontario.

Provincial police Sgt. Kristine Rae says it’s believed about 20 vehicles were involved in “numerous” collisions on Friday afternoon.

Police closed the eastbound lanes of Highway 401 and a detour was put in place around the accident site.

Rae said Friday night that the westbound lanes remained open but it wasn’t known when the highway would be reopened to eastbound traffic.

Witnesses say a number of tractor-trailers were involved and reported seeing firefighters working to extricate a driver from one rig.

Rae says the cause of the collisions remains under investigation.