Roads have reopened around Martin Place and public transport is running as normal after the area was shut down on Saturday due to a gas leak.
The NSW Government confirmed a subcontractor hit a major gas pipe while carrying out excavation works for the new Martin Place metro station.
Buses and trains are now running to normal timetables and trains are stopping at Martin Place station.
A 200-metre exclusion zone was set up, with buildings evacuated, after dangerous levels of gas were detected in the business district.
Commercial premises were evacuated and businesses were unable to open on Saturday.
NSW Transport Minister Andrew Constance has apologised for the disruption.
Authorities were called to Martin Place at 10:30pm on Friday when the gas main was hit.
On Saturday, NSW Fire Service superintendent Paul Johnstone said: "What happens when the gas mixes with a certain ratio of the air it can become explosive atmosphere and any ignition can cause a fire or explosion.
"An ignition could be some traffic lights or something similar to that in a business, a refrigerator turning on after it had been off overnight, which can cause a spark.
"And if the mixture is right it could cause an explosion." (ABC news)