Five people have been taken to hospital after a coach crashed into a ditch and overturned.
Cambridgeshire Police said the coach left the A141 near March around 6.15am.
A woman in her 50s was taken to Peterborough City Hospital with serious injuries, and a further four described as "walking wounded".
The East of England Ambulance Service said there were 65 people on the coach and 22 of them were assessed by paramedics.
Police have appealed for information about the crash and are asking drivers who saw the collision to come forward.
Sergeant Simon Goldsmith, from Cambridgeshire Constabulary, said: "I am particularly keen to speak to the driver of a yellow bus which was seen in the area at the time of the collision.
"I believe it was heading towards March, coming from the direction of Chatteris on the A141."
Anyone with information is asked to contact the road policing unit on 101 or Crimestoppers anonymously on 0800 555 111.
The A141 has been closed between Mill Hill Garage and Knights End Road and motorists are advised to avoid the area or expect delays.