Residents have been evacuated from their Newtown unit block after a fire broke out in the early hours of Sunday morning.
Firefighters arrived at the Forbes Street complex shortly after 1am to discover the common area of the building up in flames.
The cause is yet unknown.
Residents of 20 units were evacuated from the building.
By the time officers extinguished the flames, the common area was destroyed and smoke had damaged the neighbouring units.
Five residents and one Fire and Rescue worker were taken to Royal Prince Alfred Hospital for smoke inhalation, and another resident was treated at the scene.
Thirty-five residents are unable to return to their units.