The man named as Simeon Francis was arrested on May 20 in Exeter and booked into custody at Torquay Police Station, the Independent Office for Police Conduct (IOPC) said. The detainee was “found unresponsive in his cell” and an ambulance was called. He was pronounced dead at around 6pm on the same day.
The case is being investigated by the watchdog.
It said Mr Francis was 35 years old.
No cause of death was identified in a preliminary post-mortem examination.
Further tests are being carried out.
Simeon Francis, 35, died in police custody in Devon
Simeon Francis was arrested in Exeter on May 20
IOPC regional rirector Catrin Evans said: “Our thoughts are with Mr Francis’ family and friends following his death.
“We will be keeping his family updated during the course of our independent investigation.
“Our investigators have begun gathering evidence and statements from officers.
“We are analysing a considerable amount of CCTV footage from the custody suite.
Mr Francis was found unresponsive in a police cell
“We are looking at the level of care provided during the period of detention, including the frequency and adequacy of checks carried out.”
The IOPC said Mr Francis was arrested at around 12.45am on May 20 in Cowley Bridge Road, Exeter.
He was taken to the station in a police van.
At around 3am he was booked into custody.
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Simeon Francis was booked into custody at around 3am on May 20
The watchdog’s investigation comes after a mandatory referral from Devon and Cornwall Police.
An inquest into Mr Francis’s death was opened and adjourned last week by the Plymouth Coroner.
The announcement from the IOPC comes on the back of days of Black Lives Matter protests in UK cities.
Black Lives Matter protesters took to the streets of UK cities over the weekend
Street rallies were held over the weekend in London, Manchester, Cardiff, Sheffield, Newcastle, Derby, Wolverhampton, Wrexham among other cities.
While the death of the African-American man George Floyd in Minneapolis initially sparked the protests in Britain, they have since taken on a broader call for an end to racism.
On Sunday a group of protesters tore down a statue of slave trade Edward Colston.
Police in London face off with anti-racism protesters
After spray-painting it, anti-racism activists rolled it to the city harbour and dumped it in the water.
Boris Johnson said the anti-racism protests were “subverted by thuggery”.
Some protesters in central London turned violent over the weekend and 27 police were injured.
Officers were forced to run as bottles were thrown near the stone arches at the junction of King Charles Street and Whitehall.