A 25-year-old has been arrested after two men were killed in a crash on the M1.
The man, from East London, is being held on suspicion of causing death by dangerous driving.
The collision between two black BMWs happened shortly before 2.40am, near Watford in Hertfordshire.
The crash, on the southbound carriageway between junctions four and five, forced the temporary closure of a section of the M1, leading to morning traffic chaos.
The men killed, aged 22 and 24, were one of the drivers and his rear seat passenger.
Two other passengers of the vehicle, who are both men, suffered serious injuries and were taken to a hospital in London.
The four men in the second car were also injured and were taken to hospital.
Those who escaped the wreckage started fighting with the occupants of a third car that had pulled over to lay blame over the death of their friends, the Evening Standard reported.
Basit Nasir, who witnessed the crash, told the newspaper: "They all jumped out and everybody started punching each other. They said, 'What have you done? You have killed them.'
"I tried to break up the fight and called the police from my mobile."
He also said: "It was total mayhem. There was mangled metal everywhere."