The source of a gas leak that closed parts of Auckland’s CBD last night has been revealed. 

Gas and power company Vector confirmed the leak originated from a crack on an isolation valve. 

Full repairs were made to the leak overnight and while it is still unclear what caused the crack, an investigation is under way, a Vector spokesperson said. 

Emergency services evacuated sections of Auckland’s downtown area after the gas leak on Thursday evening, leaving central city streets blocked for hours. 

An emergency alert sent to mobile phones in the area at 5.45pm told people to close all doors and windows. 

“There is a gas leak at the intersection of Customs Street East and Gore Street in the Auckland CBD,” the alert said. “If you have any concerns, please call Fire and Emergency. Alternatively, evacuate the immediate area and follow instructions from local authorities. Please stay away from the area to allow emergency vehicle access.” 

Part of Customs St was cordoned off from Albert St. Beach Rd was also closed up to Anzac Ave. 

A Herald reporter said earlier in the evening that the “smell of gas is very strong on the corner of Customs and Commerce”. 

Four fire crews and support crews with gas detection equipment were at the scene alongside a Vector gas emergency response van. 

Shortly before 9pm, FENZ Deputy National Commander Brendan Nally said Vector had isolated the leak, which was earlier leaking from a manhole at the intersection of Customs St East and Gore St. 

”Gas detection equipment is being used to ensure buildings are safe to enter and the roads will remain closed while emergency services ensure the gas has dispersed. The roads will remain closed, and we continue to ask public to avoid the area,” Nally said. 

The public was urged to keep windows closed if they lived or worked near the area. 

At 10pm another emergency alert was sent to mobile phones notifying people it was safe to return to the downtown area. 

The scene in downtown Auckland on Thursday evening. Photo / Raphael Franks 

Auckland Transport had to detour buses that terminate at Britomart, which left 17 buses backed up on Gore, Fort and Commerce Sts. 

“Wake me if we start moving,” said one bus driver, forced to wait behind the cordon.