Two young girls who died after a car crashed into a roadside drainage ditch on the Norfolk-Cambridgeshire border were sisters.
The victims, aged seven and 10, died in hospital after suffering serious head injuries in the accident on the A47 near Wisbech.
The girls have been named locally as Tamzin and Jessica Portor from Sutton Bridge.
A Norfolk Police spokesman confirmed that the girls' father and their 12-year-old brother both suffered minor injuries when the Ford Focus rolled on to its side at about 6.40pm on Thursday.
Police said the car came to rest on the edge of the drainage ditch after the accident near Walsoken, around 500m north of the A47's junction with Broadend Road.
Confirming that the sisters were pronounced dead after being taken to the Queen Elizabeth Hospital in King's Lynn, the spokesman added: "The girls sadly died in hospital as a result of serious head injuries sustained in the collision.
"Their 12-year-old brother suffered minor injuries, as did their 38-year-old father, who was the front seat passenger."
The driver of the car, a 43-year-old woman who is not the mother of the children, also suffered minor injuries.
Officers said the Ford was being driven towards Wisbech when for reasons unknown it left the road and overturned, coming to rest on its side.
The A47 was closed in both directions for several hours and reopened shortly before 10.30pm last night.
Chief Inspector Chris Spinks, head of road policing in Norfolk and Suffolk, extended his sympathies to the girls' family and friends and appealed for witnesses to come forward.
The officer said: "Fatal collisions are tragic in any circumstances but given the fact that two young lives have been lost at this time of year seems to make it that much worse.
"Specially-trained family liaison officers are supporting the bereaved relatives and collision investigation officers are piecing together the events that led to the crash.
"The circumstances are still unclear at this stage and I would ask anyone who thinks they might have information, no matter how insignificant it may seem, to come forward."
Traffic police would like to hear from anyone who witnessed the incident, or who has information concerning the vehicle prior to the collision.
Witnesses should contact Sergeant Peter Howlett, who is based at Swaffham road policing unit, on 101.