Bridge Street reopens after smoke incident at Rockpool restaurant in Sydney CBD

A building fire in the CBD forced the closure of Bridge Street in both directions on Wednesday night.

Police have confirmed that the Rockpool restaurant was evacuated after firefighters were called to investigate thick smoke in a nearby laneway.

Firefighters could not locate the source of the smoke, but believe it may have been caused by electrical sparks.

Roads in the CBD are now reopened.

About seven fire trucks were called to a building on Bridge Lane at close to 9.25pm, Constable Justin Hirano said.

He said the fire brigade were responding to a call reporting a large volume of smoke coming from inside a building.

"The smoke may be from the building containing the Rockpool restaurant," Constable Hirano said.

Twenty people were believed to be inside the building, but when the firefighters arrived they had already evacuated the premises.

Kathleen McGrath, who was having dinner with a friend at the Bridge St Garage, said there were at least 12 fire trucks called to the scene that she could see.

"We had just paid the cheque, but as soon as the fire trucks arrived, a lot of people just started leaving," Ms McGrath said.

"The fire crews then arrived and told us we needed to evacuate."

She said many of the trucks were parked in front of Establishment and Mr Wongs, but she did not see any smoke or flames.

"It was difficult to tell where the fire actually was.

"But everyone was out on the streets and it was mayhem.

"It was a bit freaky, coming out on to the street and not knowing what was going on and where to go.

"The firefighters were very well organised though and the police shut off the surrounding streets and were on point."

Constable Hirano said the staff of Fratelli Fresh and Rookpool were allowed to re-enter the building to collect their things.