Emergency services were called to the home in De Lacy Street, Ashton, at around 4.15pm yesterday (Tuesday, May 25), where the man's body was discovered.
But police say they are unable to establish how he died and are currently treating his death as 'unexplained'.
Residents reported seeing a large police presence in the area around De Lacy Street yesterday afternoon, following the discovery of the man's body.
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Forensics were seen examining a phone box outside the Co-op in nearby Ripon Street at around 5pm, which police say is related to the 'unexplained' De Lacy Street death.
"The forensic examination of the phone box is part of the De Lacy Street investigation," a police spokesman confirmed.
No further details have been released at this stage, but detectives are asking anyone with information to get in touch.
A police spokesman said: "We were called at 4.17pm on Tuesday (May 25) to De Lacy Street, Ashton, to reports a man had been found dead.
"Emergency services have attended and sadly found a man in his 40s deceased.
"His death is currently being treated as unexplained."
Anyone with information is asked to call police on 101, quoting log 1093 of May 25, 2021.
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