New South Wales Police is working to identify the bodies of three people found in a house fire in Sydney’s south-west overnight.

Emergency services were called to reports of a house fire on Cornelia Street at Wiley Park about 9:45pm yesterday.

Fire and Rescue NSW (FRNSW) responded with five fire trucks and 20 firefighters.

“The crews were confronted by a ferocious fire as they arrived,” a FRNSW statement read.

“They forced their way through the burning exterior of the property, extinguishing scaffolding and garden trellis that had caught alight.

“As the firefighters entered a granny flat at the rear of the badly damaged home, they discovered the bodies of three people.”Three firefighters in protective gear wearing oxygen masks gather between a police car and fire truck.

FRNSW says it sent five trucks and 20 firefighters to the scene. (ABC News)

Extensive damage to the property was reported, with FRNSW extinguishing the blaze.

FRNSW Commissioner Jeremy Fewtrell attended the scene to provide support.

“Our investigators will examine the scene thoroughly, once it’s been declared safe,” Commissioner Fewtrell said.

“We offer our condolences to the families of the victims of this terrible tragedy.

“This is a stark reminder of the dangers of home fires, particularly during the winter period.”

A crime scene has been established at the property.

In a statement, NSW Police said it was yet to formally identify the victims, and that a report would be prepared for the coroner.