Paramedics and police were called to Clarendon Street, Landport, on Friday at 9.56pm.
Hampshire police have now confirmed an 89-year-old man was found dead.
A spokesman for Hampshire Constabulary said: ‘The incident we attended was the sudden death of an 89-year-old man at his home.
‘This death is not being treated as suspicious.’
It comes after a man in his 20s was found dead in Museum Road, Old Portsmouth by police who were called there at 4pm on Friday.
Firefighters said they attended for five hours. Police said the fire service involvement was a precaution.