Mr Walter said the building could have been destroyed if firefighters had arrived minutes later.

Firefighters attended at 68 Shoalhaven Street at 7am and saw smoke coming from the back of the unoccupied structure, used by the Catholic Diocese of Wollongong’s CatholicCare’s Children Cottage as a social services office.

Crews made their way into the building and began cooling the structure down.

Mr Walter said the building had built up a lot of heat and firefighters needed to stop a “flash over” from sparking, which they did.

“I think if we got their three to four minutes later we would had lost the entire building,” he said.

“The crews did really well.”

He said the building’s windows were just about to crack when firefighters arrived. If they had cracked, the fire would have been fuelled with more oxygen.

Mr Walter said the front of the structure showed no signs of fire but the back rooms were damaged.

Firefighters were able to confirm where the fire started and Nowra detectives, who were at the scene, are now investigating the cause.

According to CatholicCare director, Kath McCormack, no one was injured in the blaze.

“We have contacted all clients affected and have alerted them to alternative arrangements for their service.

“We are assisting the police in their investigation”, she said.