Country Fire Authority district 16 operations manager Bernie Fradd said fire investigations were on their way to the scene to determine the fire’s cause and origin. 

“Four brigades attended,” he said.

“By the time they got there the house was fully involved, so crews could only do an external attack.

“The roof collapsed very early into the firefighting.”

Mr Fradd said the house was fully destroyed but being an isolated townhouse, no other properties were threatened.

Firefighters are still on scene.

EARLIER: Country Fire Authorities are responding to reports of a building fire in St Arnaud.

VicEmergency reports CFA was called to respond to a possible building fire on Sloane Road, St Arnaud North about 10.42am.