An investigation has been launched by a police watchdog after a man died in police custody.

The Independent Office for Police Conduct (IOPC) said the 38-year-old man was pronounced dead in Leyton Custody Suite at around 8pm on September 4 this year.

The IOPC says it has established the man was detained by Metropolitan Police officers on a street in Leyton at around 5.30pm the same day and he was taken into custody.

Shortly after arriving at the custody suite at around 6.30pm, while the man was being booked in, he became unwell and then unresponsive.

Officers called for an ambulance and began resuscitation efforts prior to the arrival of paramedics, but the man passed away.

Following a mandatory referral from the Met that evening, the IOPC sent investigators to the custody suite and to the post incident procedures, where those officers involved provided their initial accounts.

Investigators have since been gathering relevant information and begun reviewing CCTV and body-worn video footage.

IOPC regional director Sal Naseem said: "My thoughts are with the man’s family at this difficult time. We have made contact with his family to explain our role and will update them as our enquiries progress.

"As the man died in police custody, we will carry out a thorough, independent investigation into all the circumstances.

"We will examine interaction officers had with the man on the street, and what happened after he arrived at the custody suite. Our investigation is still in its early stages."

HM Coroner has been informed and a post-mortem examination took place on September 7, the outcome of which was pending further tests. A date has yet to be fixed for the opening of an inquest.