There are reports of multiple casualties following a collision involving a minibus on the B1040 near Bluntisham.
Police, fire, and ambulance crews were called at about 4.50pm to Somersham Road at its junction with Bluntisham Heath Road amid reports of a two-vehicle collision.
It is understood that a minibus was involved and about 15 people are said to have been injured.
A spokesman for Cambridgeshire police said: "Multiple people are involved and some are seriously injured. The roads going in either direction at the junction have been closed and motorists are advised to avoid the area."
A spokesman for Cambridgeshire Fire and Rescue Service said more than 20 firefighters had been called to the scene.
The spokesman said: "More than 20 firefighters are at the scene of a road traffic collision with police and ambulance crews on the B1040 at the cross roads with Somersham Road and Bluntisham Heath Road, the road is closed in all directions so please avoid the area."
The East Anglian Air Ambulance and a team from the East of England Ambulance Service were also at the scene, with the injured being taken to Hinchingbrooke and Addenbrooke's hospitals.
A spokesman for the ambulance service said: "We are at the scene of a serious collision near the B1040 near Woodhurst. Our hazardous area response team is there along with a number of ambulances. We are treating approximately 15 patients."
Anyone who witnessed the collision is asked to contact the road policing unit on 101 or visit www.cambs.police.uk/report.