SYDNEY, Feb. 13 (Xinhua) -- A major blaze broke out at the construction site of a high-rise building downtown of Australia's New South Wales state capital Sydney on Tuesday morning, with 20 fire crews deployed and 13 people treated for minor smoke inhalation, according to authorities.

Firefighters were alerted to the blaze at 08:43 (AEDT) at the black net-meshing covered building in the Circular Quay harborfront area and contained the fire, which was still active two hours later, a state fire and rescue spokeswoman told Xinhua.

"When they responded, the mesh or the scaffolding on the exterior was alight, but the fire is also inside what appears to be a construction area," she said.

"All persons were evacuated and we set up an exclusion zone surrounding the site."

Paramedics treated the 13 people at the scene and others in the area were urged to leave due to the amount of smoke and wind, a state ambulance spokeswoman told Xinhua.

The cause of the fire has yet to be determined but local media reported that gas cylinders at the site exploded and startled nearby pedestrians. Train, bus and ferry services were also temporarily disrupted.

The site is part of a planned mixed-use development that includes high-rise apartments, according to local reports.