After being detained by Derbyshire Police, a father-of-three died in hospital.
Police have yet to identify the individual. He was identified locally as Chad Allford, 23 years old.
The father-of-three is understood to have been arrested by officers at an address in Alfreton shortly before 5pm on Wednesday before becoming unwell.
He was then taken to hospital by ambulance. However, he later died, according a police statement.
Following the incident, the force referred itself directly to the Independent Office for Police Conduct.

Chad Allford, 23 years old, has been named as the victim of police custody. On social media, tributes pour in for him

On the pavement near the entrance to Morewood Drive, Alfreton, were written messages for Chad titled “RIP Chad”
A spokesperson for Derbyshire Police said that officers responded to a call at Morewood Drive in Alfreton just before 5pm on Wednesday.
“A 23-year-old man was taken into custody after becoming ill. He was taken to the hospital by ambulance and later died.
“The force has referred itself the IOPC.
A spokesperson for IOPC confirmed that an investigation into the incident was in its very early stages.
A statement continued, “The IOPC has begun an investigation after a man aged 23 died following contact with police at a residential address in Morewood Drive. Alfreton. Derbyshire on Wednesday.
“At around 5pm, Derbyshire Constabulary police officers detained a man who became increasingly unwell. He was taken to the hospital, where he later died.

Alfreton Police officers at the scene in Moreland Drive. This is where Mr Allford was detained on Wednesday evening.

A police cordon has been established around the property. Derbyshire Police has referred itself the standards watchdog after the incident
“The matter was referred to the IOPC and investigators attended the scene and the post incident procedure yesterday to being enquiries.
“Our independent investigation in the very early stages.”
Since then, tributes have flooded in for Mr. Allford via social media.
Harry Lacey-Hatton said in a Facebook post: ‘Really can’t believe it. You were one of the most kindest boys growing up.
‘I’ll never forget the times we had mate. You always stuck up for me in school and I’ll always be grateful to you for that cuz. Doesn’t seem real.
‘Rest in peace Chad Allford my thoughts are with your family & little boy.’
Ryan Minkley stated, “Enjoy each day because a wise person once said yesterday was gone and tomorrow is not a promise.
‘R.I.P Chad Allford.
Aaron Lunn posted: “Rest in Peace Chad Allford. Had a lot good times growing up.
After his death, many social media posts included a #JusticeForChad tag.