An inquest has been opened into the death of a 36-year-old mother-of-three whose car crashed off the A47 and hit a tree.

Catherine Piercy - known to her friends as Kate - of Dereham Road, Norwich, was driving a red Citroen Berlingo which went off the dual carriageway at Dereham at about midday on Sunday.

The front seat passenger was her husband - who is in his late 30s - and he suffered serious head injuries and multiple fractures.

He is in a critical but comfortable condition in Addenbrooke's Hospital in Cambridge.

Their 10-year-old son - who was a back seat passenger - suffered serious head injuries and is in a comfortable and stable condition at Addenbrooke's.

Their two other children - a 12-year-old girl and a five-year-old boy - were also rear seat passengers and received slight injuries and were treated at the Norfolk and Norwich University Hospital before being released.

Police have not released the names of the other members of the family or said what part of Norwich they are from.

Norfolk coroner William Armstrong opened the inquest into the death of Mrs Piercy, who was originally from Chelmsford, and adjourned it while police investigations continue.

The car was travelling in the Swaffham bound lane and just before the slip road to the A1075 and the Tesco store it appeared to swerve and then went off the road and hit the tree.

No other vehicles were involved.

Police are continuing to investigate the cause of the crash and have put signs up around the site appealing for information.

PC Ian Thexton from the serious collision investigation team wants to hear from anyone who saw the collision or the manner of driving of the Citroen before the incident.

He can be contacted on 0845 456 4567.

Family liaison officers are with members of the family and a spokesman said they were 'understandably traumatised' after the crash.

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.