A woman in her late 30s was killed, her husband is critically ill in hospital and her 10-year-old son is being treated for serious head injuries after their car crashed into a tree.

Police have revealed it was five members of the same family from the Norwich area who were in the red Citroen Berlingo which went off the A47 Dereham Bypass at about midday on Sunday.

The couple's two other children - one aged 12 and one aged five - received slight injuries and were treated at the Norfolk and Norwich University Hospital before being released.

Police said the mother was driving the car and her husband - also in his late 30s - was a front seat passenger. He is in a critical condition in Addenbrooke's Hospital in Cambridge with serious head injuries and multiple fractures.

Their 10-year-old son was in the back of the car and suffered serious head injuries and is also being treated in Addenbrooke's Hospital.

No further information about the family has been released.

Police said the car was travelling in the Swaffham bound on lane a and just before the slip road to the A1075 and the Tesco store, the car left the road and hit a tree.

Police are appealing for witnesses to the crash.

PC Ian Thexton, of the serious collision investigation team can be contacted on 0845 456 4567.

The crash left the Swaffham-bound carriageway of the A47 blocked at the turn-off to the town by the Tesco supermarket for nearly four hours.

Traffic was being diverted off the road at the Swanton Morley junction and through the town along Norwich Road.

Traffic queues of about two miles built up.

At least four police cars, two fire engines from Dereham, three ambulances and two paramedic cars attended the crash, as well as the air ambulance.

Police spent several hours at the scene carrying out detailed investigations in to what caused the crash.