Three vehicles collided on Highway 400 in North York Thursday evening, seriously injuring one woman.

The crash happened on the southbound lanes of the highway near Finch Avenue.

Toronto Fire said one person was extracted from a vehicle.

A woman, believed to be in her 40s, was rushed to a trauma centre in serious, possibly life-threatening condition, paramedics said.

The cause of the collision is unknown.

All southbound lanes of the highway at Finch Avenue are closed due to the crash.