Emergency services were called to Buist Street in Bass Hill at 11.20am when another resident at the property found the man, who is thought to be in his mid to late 60s.

Paramedics were called, but the man could not be revived. His death is believed to be suspicious.

A police was launched at the home, which remained underway on Friday afternoon.

Police could be seen conducting a search of the nearby area, including checking in gutters and down stormwater drains.

Officers walked in a line on a nearby field as they looked at the ground. Forensic officers, wearing blue protective suits, walked in and out of the house.

Chief Inspector Glen Fitzgerald from NSW Police said the man's body had "obvious signs of injury" and the crime scene had been "locked down".

"A forensic examination is currently underway and until such time as that has been completed, the cause of death and any further injuries related to that are unknown and being established," Mr Fitzgerald said.

The man was one of four people who lived in the shared rental property, police believe. He was seen alive in the house on Thursday night by another person who lived there, before he was discovered this morning.

There were no reports of fighting or screaming in the area in the time he is thought to have died, police said, and the man was not known to them.

"I must stress that we still are confirming his identification," Mr Fitzgerald said on Friday afternoon. "At the moment, police are treating the death as suspicious."

Anyone with information on the man's death, or who may have seen suspicious behaviour in the area in the early hours of Friday morning, has been urged to contact Crime Stoppers on 1800 333 000.

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