A force is facing investigation after a man had a cardiac arrest and died after being restrained by police officers.

The Independent Office for Police Conduct (IOPC) said Thames Valley officers initially took the 24-year-old to hospital after having responded to a disturbance on 27 January. As he was discharged into custody later that day, he was restrained by officers and then suffered a cardiac arrest.

Thames Valley Police said it would be “fully co-operating” with the inquiry.

After the cardiac arrest, the man was taken back to hospital and put in an induced coma. The IOCP was informed and an investigation was started on 28 January. The man died in hospital on 2 February.

The IOPC said the man, from Milton Keynes, was first detained by officers as they responded to reports of a disturbance.

Officers took him to hospital after being told of “medical concerns” about the man, and he was discharged into police custody later that day.

The IOPC said its evidence suggested at that point “there was an incident that led to him being restrained by officers”. “After being taken to a police vehicle he suffered a cardiac arrest and was returned to the hospital where he was placed in an induced coma,” the IOPC said.

Graham Beesley, its regional director, said: “We have a duty to investigate in these circumstances and in particular we are looking at the contact that police officers had with the man prior to his death. “We have contacted the family to explain our role and we will keep them regularly updated throughout our inquiries.”

Thames Valley Police said it was “fully co-operating” but due to the investigation it would “not be appropriate” to comment further. Investigators have gathered police body-cam and hospital CCTV footage, and taken accounts from officers involved, the IOPC said.

The coroner’s office has been informed and an inquest is due to take place, it added.