Drivers are being warned to expect long delays following a collision between a motorcycle and a lorry in Buckden.
The accident occurred at 9.15am on the A1 Great North Road between the Buckden Roundabout and Stirtloe turn off.
A spokesman for Cambridgeshire police said: “We were called at 9.15am to reports of an accident involving a lorry and a motorcycle.
“Injuries have been reported but details are sketchy at this time.”
The stretch of road has been closed on the southbound carriageway while emergency services attend the scene.
Motorists are being advised to use alternative routes if possible.