An investigation was under way after one person died and four others were injured when their car crashed into a brick wall after a police pursuit.
The Independent Police Complaints Commission said officers in a police patrol car saw a Mazda with five young people being driven erratically through the Bevendean area of Brighton at about 1am on Saturday and signalled for it to stop.
The driver did not respond and, after a pursuit the vehicle crashed into a brick wall, killing one passenger and leaving another critically injured.
All five were taken to the Royal Sussex County hospital, where one has since been discharged.
Police confirmed they have arrested the driver of the Mazda.
A spokesman for East Sussex Fire and Rescue, who attended the incident, said at least two occupants of the car were thrown out of it in the ferocity of the crash.
Formal identification has not yet taken place and the IPCC said they would not be releasing any names until next week.
IPCC Commissioner Tom Davies said: "My condolences go to the family and friends of the dead man. This must have been a traumatic incident for everybody involved, including the members of the emergency services who attended.
"The IPCC investigation will be independent and proportionate."
