Firefighters responded to an incident on Bridge Rd in Melton South at 5.16pm following multiple calls to Triple Zero (000) reporting a house fire.
Fire Rescue Victoria arrived on scene, finding a single-storey brick building fully involved in fire.
The roof of the building had collapsed, and external firefighting was aggressive.
A community warning was issued for smoke in the area, and some evacuations were undertaken.
The building was an old, abandoned nursing home.
No injuries were reported.
The cause is yet to be determined.
