Two people have died and another two are in a life-threatening condition after a car crashed into a tree in Loughton, Essex.
Police said the two victims who died were a 21-year-old man and 16-year-old girl.
The other victims currently in hospital are two girls aged 16 and 17, Essex Police said.
A 21-year-old man from Loughton was arrested at the scene on suspicion of causing death by dangerous driving, causing serious injury by dangerous driving and perverting the course of justice.
He was taken to hospital, where he is being treated for what are believed to be minor injuries.
Officers found a silver BMW M3 had collided with a tree in the Goldings Hill area of Loughton, shortly after 2.05am on Saturday.
No other vehicle was involved.
Essex Police are appealing for witnesses who saw what happened, or saw a silver BMW M3 driving in the Loughton and Epping areas in the early hours of Saturday.
Police are also keen to speak to anyone who was driving in the area who has dash cam footage, or anyone who has CCTV.
Witnesses are asked to contact the Serious Collision Investigation Unit on 01245 240 590 or email CollisionAppeal@essex.pnn.police.uk.
Alternatively, contact the Crimestoppers charity anonymously on 0800 555 111 or use the anonymous online form at Crimestoppers-uk.org.