Ammonia gas leak at Hamilton meat factory

File photo / NZ Herald

Firefighters have isolated an ammonia leak in a Hamilton meat factory which has shut down the North Island main trunk line and drawn more than 40 firefighters, police and St John Ambulance to the scene.

The leak at the Goodman Fielder meat factory in the industrial suburb of Frankton was discovered after 10am and 10 fire appliances are involved in the mass response.

Fire Service Waikato area commander Roy Breeze said the risk of an explosion was low and the need for evacuation was not necessary yet.

"We've just found it. The guys have isolated it now and it's just a matter of trying to work out how to ventilate the gas that's in the system."

Hazmat firefighters in level four suits had entered the large building, where stuffed cheeses and meat were being stored, to investigate.

Mr Breeze said the Fire Service ordered the shut down of nearby railway lines because of the leak but they would likely reopen soon.

"All of this is a high level of precaution and that's what we're here for."

He did not know what had caused the leak yet.

Police and St John's staff were on standby at the Lincoln St address.

Police said as a result of the gas leak the southbound slow lane on State Highway 1 has been closed, and traffic is expected to be congested.

- additional reporting APNZ