A number of Britons were injured when their coach crashed in Kenya, the Foreign and Commonwealth Office (FCO) has said.
The incident happened in the coastal city of Mombasa at around 6am on Saturday.
Eyewitnesses described how the vehicle rolled down an embankment on to another carriageway which had oncoming traffic.
Mark Bizley, who was travelling behind the coach, told BBC Radio Solent: "Its wheels lost grip on the tarmac and it started to snake. I could see the driver was really struggling to keep the vehicle straight. His right-hand wheels went over the edge of the tarmac and as soon as the wheels left the road the bus rolled.
"That side of the coach stopped snaking and the forward momentum turned the bus over and it rolled down the embankment into the other carriageway, which was busy."
An FCO spokesman said: "We are aware of the bus crash in Mombasa. Our team in Mombasa is providing consular assistance to the British nationals who have been affected.
"We are working very closely with the tour operator, Thomson. Some British nationals remain in hospital receiving treatment for injuries, accompanied by their families. The remaining passengers will be leaving Kenya."
Around 15 people were believed to have been on the coach when it crashed. The number of Britons involved is not yet known.