A house was destroyed by fire on Casino Street, South Lismore, early this morning.

NSW Police told the Lismore App a 27-year-old female was treated for minor injuries, and the cause of the fire was accidental. No further investigation will be carried out.

Lismore Station Officer for Fire and Rescue Ian Grimwood said they were told the occupant was in a back lane at the back of the house when the first unit arrived.

"I got notification when we first arrived, and then a police car pulled up. We were pretty busy at that point trying to contain the fire."

The house was at number 10 and is believed to be the old Lismore Police Station, built around 1910.

"It took a couple of hours to extinguish. The house was destroyed, but we managed to save some of the rear and some of a shed at the rear of the property," Mr Grimwood said.

"There was a steel fabrication shed next door which suffered minor damage along with a house next door as we used water to stop the main fire spreading."

There were reports of further smouldering this morning, with Fire and Rescue called again.

"You often get cedar continuing to smoke under the tin roof, which takes two or three goes to put out completely. It is difficult to put a fire out 100% immediately. We had a crew back out this morning."