SHOCKED commuters travelling to work have captured the inferno from a building in Circular Quay this morning. A fire operation is underway.
Olivia Mocevakaca, 26, was working on the wharf when the explosions shook the wharf about 8.50am.
"When I heard the first boom it was massive it shook the wharf," she said.
"It started at around 10 to 9am."
"It shook the wharf ... there were four explosions and it shook the wharf
She rushed out to see what the commotion was and saw fireballs dropping from the sky.
"There was fireballs from the top falling to the ground."
"It really did vibrate the whole area, we thought a train had crashed.
Eye witnesses have described hearing loud bangs from the multistorey building.
Rossini waitress Jenny-Emilia Seidel, 18, said she heard "three explosions" as the building overlooking her restaurant went up in flames.
"The building was completely on fire and they were trying to put it out when I heard three explosions," she said.
"This was just after 9am and it was very loud.
"At the moment we are shut because the police told us to close so we don't know what's going on."
Circular Quay beside Gateway. Construction site on fire. pic.twitter.com/pk3XIbffyP— Jono P (@Jono5785) February 12, 2018
There is a 200 metre exclusion zone around where the building fire and police have taped off nearby streets.
Ammette Yazbek was working in the Big Bus company in Circular Quay Station when she noticed people running from the area.
Nearby workers heard a series of explosions.
"I saw everyone walking away and then I saw everyone taking photos."
"A couple of times we've heard what sounds like an explosion, but I am not sure if it is part of the building ... but there is a strong smell of gas
"It is affecting George Street and they have made them move.
"You can still smell the gas but it was really strong before.
One rail workers said saw the series of explosions in the building and saw the whole construction site erupt in flames.
"I was working outside. It was like fireballs exploding and then the whole building was on fire," he said.
"Within half an hour it started to be massive."
There is a building site on fire at circular quay. pic.twitter.com/BH9btG4B80— brad esposito (@braddybb) February 12, 2018
Police have declared the fire an emergency situation and evacuated nearby businesses.