On Friday, chlorine seeped from a gas bottle and on Tuesday liquid ammonia was detected.
Fonterra general manager operations lower South Island Richard Gray says the company is investigating.
“These are two unrelated incidents, relating to two very different processes. We are investigating the root cause and will be putting in place appropriate measures to help prevent these incidents reoccurring,” Gray says.
On Friday, about 3.50am, three fire crews responded to a chlorine leak at the factory.
A fire service spokesman says fire trucks from Edendale and Wyndham attended, as well as the Invercargill specialist decontamination unit.
The fire crews provided decontamination and left the situation in the hands of Fonterra staff, he says.
A St John spokesman says ambulance staff were not required.
A Fonterra spokeswoman says a valve on a chlorine gas bottle had a leak, which set of the alarms.
The bottle was stored in a small enclosed shed on the north-west side of the site.
The leak was not near production facilities, the spokeswoman says.
The factory was in production at the time and was not evacuated, she says.
About 12.55pm on Tuesday, Edendale fire fighters responded to a report of an ammonia leak.
When they arrived, Fonterra staff had isolated the leak.
A Fonterra spokesperson says the ammonia did not contaminate any food products.
“We are investigating the cause of the leak.”
The factory’s monitoring system detected vapours from the leak, the spokesperson says.
“We took the precautionary action to evacuate the plant and things were back to business as usual within two hours.”