A motorist has been detained on suspicion of causing death by dangerous driving after a rush-hour pile-up in which four people were killed.
The crash, which closed a section of the A34 in Berkshire for several hours, involved four heavy goods vehicles and four cars.
Police confirmed four people died at the scene, while a man was taken to the John Radcliffe Hospital in Oxford with life-threatening injuries and two other people were taken to the Royal Berkshire Hospital with minor injuries.
Nine other people who were slightly hurt were treated at the scene following the accident near East Isley, close to the M4, which happened shortly after 5pm on Wednesday.
A Thames Valley Police spokesman said: "A man has been arrested on suspicion of causing death by dangerous driving and is currently in custody."