The cause of death of a prisoner found unresponsive at Forest Bank remains unknown, an inquest heard.
Jonathan Paul Pisani, 46, was discovered by his cellmate at the Salford jail on Wednesday 19 January.
An inquest opening at Bolton Coroner's Court heard that Mr Pisani had been seen 'alive' and 'well' the night before.
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He had been recalled to prison for breaching licence conditions after serving time for possessing a firearm with intent to endanger life.
Police Coroner's Officer, Julianne Hyde, told the hearing: "On the 19th January 2022 Jonathan Pisani was found deceased in his shared cell by his cellmate.
"He had been seen alive and well the evening before and he’d gone to sleep.
"When the nurses arrived the following morning to give medications, Mr Pisani was unresponsive and was declared deceased at the scene by the doctor on call."
A provisional postmortem examination was carried out by Home Office Pathologist, Dr Charles Wilson, following the death.
Mr Wilson concluded that the cause of death was unascertained pending histology and toxicology results.
Greater Manchester Police confirmed they were called to the Agecroft prison and carried out enquiries.
There are not believed to be any suspicious circumstances surrounding Mr Pisani's death, they concluded.
The category B prison has capacity for 1,460 prisoners and is run by Sodexo Justice Services.
Senior Coroner for Bolton, Timothy Brennand said he had received confirmation from the Prison Service Ombudsman that a formal investigation into the death is being carried out.
"This is a state detention death and we will need to await the cause of death before we can determine if this is an inquest with a jury or without," he said.
"It is highly likely this is a case that will be heard much later in the year."
In a previous statement, An HMP Forest Bank spokesperson said: "We can confirm that a prisoner sadly died at HMP Forest Bank on Wednesday, 19th January 2022.
"It would be inappropriate to comment any further at this stage."
The hearing was adjourned for a pre-inquest review which is expected to take place on April 29.