On top of the building, workmen were spotting casually strolling to the other side of the building to evacuate the space - you can see the footage in the video below.
The cause of the blaze is not yet known, but several witnesses reported hearing bangs and explosions, and one witness told Ten Eyewitness News officials evacuating the area said the cause of the fire may have been a gas leak. The sale extended a global asset sell-off to fund debt repayments, following increased government scrutiny on moving money out of China.
The fire broke out in Circular Quay at about 8.45am.
No trains were stopping at Circular Quay station due to the blaze, and motorists were also being advised to avoid the CBD area around Pitt Street, Alfred Street and Bridge Street.
CLARE MASTERS Fire breaks out at a construction site in Circular Quay
A 200-metre exclusion zone was set up as thousands of office workers watched on.
A building at Circular Quay has been engulfed in flames after an explosion on the ground floor, according to reports.
"The plastic sheeting on the outside caught on fire and dropped down onto a forklift".
Thirteen people were treated for minor smoke inhalation, a NSW Ambulance spokeswoman said.
Trains have resumed normal services at Circular Quay, St James and Museum, after being shut down briefly because of the smoke.More news: Barclays Bank charged over £2.2bn Qatar loan