An investigation has started into why a man died after being restrained by police officers and “becoming unwell” in their van.
The 32-year-old man died on Tuesday in hospital, where he had been since the incident two days before.
Officers were called to an incident in Ryecroft, Haywards Heath, shortly before midnight on Saturday and approached the man, who was leaving the area.
The Independent Police Complaints Commission (IPCC) said he “became unwell” minutes later after being restrained and put in a police van shortly after midnight.
Officers took him out of the vehicle in South Road and performed CPR before an ambulance took him to hospital.
The results of a post-mortem to establish the cause of his death have not yet been released.
Sussex Police referred the investigation to the IPCC, which has sent officials to examine the scene and take statements from the officers involved.
"The IPCC will carry out a robust and thorough investigation into the circumstances and nature of his contact with the police, the events leading up to his becoming unwell and his hospitalisation."
The man has not been identified but the IPCC said it had met with his family about the investigation.
House-to-house enquiries were made and the watchdog is continuing to appeal for witnesses to the incident in Ryecroft or South Road to get in touch by calling 0800 015 4877 or emailing email@example.com.