Police investigating a motorway crash on Christmas Day in which two young brothers were killed have described the incident as "unimaginably sad and tragic".

Officers continued to appeal to the public for help in piecing together what happened when a red Ford Focus crashed on the M6, killing three of the car's five occupants.

Two of the passengers were brothers - aged four and 10 - while a 32-year-old woman, believed to be from the Thames Valley area, also died.

The boys' mother, who was driving the car, was injured and taken to hospital but has since been discharged.

Chief Superintendent Martin Evans, of the Central Motorway Policing Group (CMPG), said: "The thoughts of all officers and emergency services colleagues involved are with the bereaved families at this extremely difficult time, and specially trained family liaison officers have been appointed to support them."

The police force said that the crash was described by investigating officers as "unimaginably sad and tragic".

Another female passenger in the car was also injured and taken to hospital after the crash, near junction 15, close to Stoke-on-Trent, at 11.25am.

That passenger and the boys' mother spent the night in the care of doctors at the University Hospital of North Staffordshire in a stable condition, and were well enough to be discharged.

The crash shut the M6 for much of Christmas Day, to allow emergency services - including three ambulances and two air ambulances - to reach the scene.

No other vehicles are believed to have been involved in the accident, and the circumstances surrounding what caused the crash are now being investigated by the CMPG.