The arson squad will investigate a suspicious fire at a heritage listed building in the CBD.

Firefighters spent an hour putting out the blaze at an abandoned building on the corner or Milligan Street and Murray Street this morning.

The fire started at about 1.30am and there has been significant damage to the first floor of the building

The Hostel Milligan facade dates back to the 1930s, with parts of the building’s interior built in the late 1800s.

Parts of Milligan Street and Murray Street were blocked off this morning, but authorities have now reopened the roads.

Police say the cause is suspicious and the arson squad will investigate what sparked the blaze this morning.

Police have taken a women in for questioning over the suspicious fire.

Anyone with any information is urged to contact Crime Stoppers on 1800 333 000.

(Photo: Kelly Haywood/ Nine News.)