At least four people have died after a crash involving several vehicles, including a lorry, on the M5 motorway.
Avon and Somerset Police said the collision happened between junction 16 near Almondsbury in south Gloucestershire and junction 14 near Falfield.
The force said: "Sadly, at least four people have died."
The motorway is closed in both directions after the crash which happened at around 2.30pm on Saturday.
Police said the motorway would be closed for "a considerable amount of time".
An image posted to Twitter showed a lorry, which had crashed off the northbound carriageway, surrounded by emergency service vehicles.
Cardiologist Amer Hamed, who was in a car travelling "10 to 20 seconds behind" the crash, told the BBC: "There was a lorry involved and at least two other cars. One was absolutely destroyed and another had flipped over."
Along with other medically-trained motorists, he stopped to help an injured woman.
Dr Hamed added: "People are helping as much as they can. Several people offered us water and one man came out of his car to give food. We're going to be stuck here for a few hours yet."
Highways England said traffic queues stretched for around six miles.