Ontario provincial police said a vehicle collided in the lanes of the Niagara Expressway near Ford Drive.
The vehicle veered off the highway and ended up on North Service Road, colliding with a fence, police said.
One person was taken to hospital in danger of death.
The cause of the crash is unknown.
Police closed the QEW lanes to Niagara Falls on Ford Drive and the west lanes of Highway 403 on Upper Middle Road.