Two prisoners died in custody at HMP Ranby in Nottinghamshire on Wednesday, the Ministry of Justice confirmed. The Category C training and resettlement prison is near Retford.
Nottinghamshire Police said it had launched an investigation and was working with the Prison Service to establish the circumstances surrounding the deaths. Detective Inspector James Oakton said the families were being supported.
The Prison Service said the Prisons and Probation Ombudsman would investigate the deaths, as it does in all cases involving deaths in custody, and that it would respond to the findings in due course.
East Midlands Ambulance Service confirmed it had attended HMP Ranby on both Wednesday and the following day. It declined to comment further while the investigation is ongoing.
Sources: BBC News UK.