By Thursday afternoon, the blaze had been extinguished.

With extensive damage to the townhouse, in particular the bottom floor, the property has been deemed uninhabitable and the residents have been temporarily relocated.

A firefighter from the scene said the home was "severely damaged" by the blaze.

"We've since blocked off the property and investigations are underway to determine the cause and exact location the fire began," he said.

EARLIER:

THERE were large volumes of smoke billowing from a house fire in Mayfield on Thursday as crews tried to gain control of the blaze.

About 2pm residents called Triple-0 to alert the authorities of smoke coming from a property on Corona Street.

A two-storey residential building was ablaze when firefighters arrived on scene.

A spokesperson for NSW Fire and Rescue has said the fire was still ongoing at 3pm and teams were working to locate the source of the blaze. It was believed that all occupants were safely out of the home.

"There's six crews currently at the scene," he said.

"While the cause of the fire is currently unknown, the smoke is being ventilated from the building in an attempt to locate the source."

Police and paramedics were also called to the scene.

A spokeswoman from the NSW Ambulance team said no injuries had been reported.

"We've sent two crews to the scene, where two patients were assessed," she said.

"They were cleared with no need to transfer or commence further treatment. We're at a precautionary stage currently."

No further details have been released at this time.