Police are investigating the death of a 40-year-old man whose body was found at the Stuart Flats in Griffith early on Thursday morning.

A forensics squad had closed off Block 8, on Light Street, with police tape and were still at the scene late on Thursday. Wearing white jumpsuits, they appeared to be working on more than one floor of the building.

Blood could be seen splattered on the walls through a second-floor window of the four-storey building.

The cause of death has not been determined and police say an autopsy will not be conducted until Sunday at the earliest.

John, a resident of Block 8, was sitting at a picnic table opposite the building on Thursday evening with other neighbours.

He said he been visiting his mother for Christmas and returned to the flats about 10.30am to find the building cordoned off with police tape.

John said he had not been able to get access to his flat and at 6.30pm was still waiting to be allowed back in.

ACT Policing was unable to say who found the body or provide any further details.