Two children are believed to have suffered serious injuries after a crash on the A689 between Burn Road roundabout and the B1277 roundabout in Hartlepool.
Cleveland Police have confirmed the road is still closed while they recover vehicles.
The emergency services are still on scene.
A spokesman said the two children have been taken to James Cook Hospital in Middlesbrough, with one airlifted to the hospital and the other child taken by road.
The adult involved has also been taken to hospital.
Hartlepool Stranton Fire and Rescue Service have confirmed one child had been taken to James Cook Hospital by air ambulance.
A spokesman from the station said that when they were called to the scene at 2.33pm the three occupants of the car -one woman and a boy and girl under the age of 12 - were standing by the roadside.
The fire service believe the car was in the outside lane of the road when it collided with a fence and flipped over.
One engine from Billingham and two from Hartlepool were on scene and assisted paramedics before leaving at 4.30pm.
The A689 between Burn Road roundabout and the B1277 roundabout in Hartlepool is expected to remain closed for a number of hours following an incident involving a black Fiat Punto at around 2.25pm this afternoon.
Two children are believed to have suffered serious injuries in the incident and are currently being treated by medical staff.
The Great North Air Ambulance is currently on scene along with Cleveland Police and Hartlepool Fire and Rescue Service after reports of a car which has rolled over on the road.
An Air Ambulance spokeswoman said they were called at 2.30pm and expect to air lift one person to hospital but details of the injuries is not known at this time.
More details to follow.