Workers evacuated after ammonia leak at Fonterra Te Rapa

Workers at the Fonterra Te Rapa site in the Waikato have been evacuated after an ammonia leak this morning. Photo / David Kerr

Emergency crews are at the scene of a huge ammonia gas leak at a Fonterra site in the Waikato early this morning.

Up to 20 firefighters are responding to the scene at the Te Rapa plant near Horotiu after reports of a leak at 2.30am.

Fire and Emergency NZ confirmed workers had been evacuated in the early hours of this morning.

Northern fire communications shift manager Colin Underdown said the leak was initially in liquid form before it turned into a gas leak.

"It's the gas that's dangerous - that you could walk into and die," he said.

A large ammonia cloud is now hovering over the area.

Police said staff are on standby, but that no moves have been made to close off roads at this stage.

Fire crews are at the Fonterra Te Rapa site, north of Hamilton, after a large ammonia gas leak early this morning. Image / Google Maps

There were no injuries reported at the site, Underdown said, and there had been no evacuations of any residents in the area as the plant was somewhat secluded.

A Fonterra spokeswoman said the leak happened about 2am.

All of their staff were safe and they were working to establish the cause of it.

"The Fire Service is managing the situation and conducting a safe release of the gas, which is a visible cloud," she said.

The spokeswoman said there was no impact to the site's operations systems as it is under maintenance at the moment.

Fire crews on the ground reported that it could take "several days" for the situation to be brought under control, Underdown said.