Two children were airlifted to hospital after a road accident in Seaham.
The collision, between a car and bus, closed the A182 between the A19 and Fox Cover Industrial Estate.
Station manager Fraser McGuffog, from Seaham fire station, said firefighters had used hydraulic cutting equipment to free the driver from the car.
The others had been released by ambulance crews.
A North East Ambulance service spokeswoman confirmed two people had been taken to hospital with head injuries, one with a pelvic injury and one with a suspected spinal injury.
All four were taken to Middlesbrough's James Cook Hospital. A two-year-old and a ten-year-old were flown by the Great North Air Ambulance, while the woman and the third child were transported by road.
All patients were believed to have suspected serious injuries but a Durham Constabulary spokeswoman said they were not thought to be life-threatening.
The road has now reopened.