Vector gas authority is working with firefighters in digging holes either side of the leak in attempt to stop it.
New Zealand Fire Service assistance area commander Jeff Maunder said one of two main gas lines the run the length of Waihi Rd was ruptured at 9.30am by a digger.
Emergency services were warning people to avoid any naked flames until advised otherwise.
''We have a natural gas leak, that's obviously a flammable risk,'' Mr Maunder said.
Mr Maunder said the road was likely to be closed for about an hour as emergency services and Vector work on the leak.