Motorists are being urged to avoid the A16 near Dogsthorpe in Peterborough following a fatal collision.
The crash between two vehicles, a Vauxhall Vectra and Land Rover Discovery, was reported at just after 4pm.
One person is understood to have been killed in the collision and a second has been taken to Peterborough City Hospital.
There are long delays in both directions on the A47.
The East of England Ambulance Service was called at 4.08pm to the A16 southbound. A spokesman for the service said: “A rapid response vehicle and ambulance crew are at the scene and that they are aware of four patients, but at this stage they do not have any more details.”
Anyone who witnessed the collision should contact the road policing unit on 101.