Sussex Police are carrying out a planned excavation at Anston House, Preston Road, Brighton.
It is part of an investigation into a recent claim that part of a human skeleton was present at the site when the building was erected in the 1960s.
Police say that they will attend to determine whether there are remains there, and if so, will work with specialists to analyse the bones.
Police seen at the site of Anston House
At that point they would hope to determine their age and whether there are any suspicious circumstances.
Following the police excavation, there is a planned archaeological dig at the site and members of the public will not have access for a number of days.