The explosion knocked out the wall of a second-storey unit on Clarence Street at about 6.30am.

NSW Fire and Rescue Superintendent Adam Dewberry said there had been “significant damage”.

“The wall, a double or triple brick wall, has literally blown out of the building off that second level,” Dewberry told Today.

“Now, that explosion also causes a significant pressure wave, which is where the neighbouring properties and buildings have also felt that shockwave.”

Falling rubble destroyed a car parked below.

Firefighters carried one male out of the wreckage, and that person has since been taken to hospital.

“Our focus at the moment is continuing to do a search to make sure we get an all-clear, good, everyone accounted for, which we haven’t got at this stage, but we’re working through it,” Dewberry said.

“But it is still a very precarious and dangerous situation for our firefighters to move in and around.”

Nearby resident Charlton said he was having “a nice cup of coffee” when the explosion happened.

”And then I heard these two loud bangs, and then I said, ‘my god, it’s like an earthquake going on somewhere’,” he said.

“So I went down and I saw this whole building come down … very scary.”