Seven Fonterra workers treated after a toxic fumes scare today have all been discharged from hospital, and five have already returned to work.

A pipe being cleaned with bleach sprang a leak and created toxic fumes at a South Island factory this morning, the dairy co-operative said.

Emergency services were called to Fonterra's Clandeboye plant north of Timaru about 11.15am.

Some suffered a mild shortness of breath, Fonterra spokesman Steve McKnight said. Oxygen was made available to three workers who needed it and the workers showered as a precaution.


There were no marks evident on the skin, and none of the six men and one woman suffered runny noses or weepy eyes, which can sometimes happen in fume events.

Five returned to work after the precautionary visit to Timaru Hospital, and the remaining two will be back at work tomorrow, Mr McKnight said.

There had been a leak of sodium hypochlorite - bleach - while a cheese-making section was being cleaned, a Fonterra spokesman said earlier.

"It's used as a sanitiser which kills everything that's left over. We're still investigating but there has been a leak from a pipe and that has generated some fumes."

The factory and an adjoining administration area were evacuated. There was no product in the plant at the time, the spokesman said.

South Canterbury District Health Board communications advisor Nicola Pearce said hospital staff had protective equipment and a decontamination shower available should it be required. The patients were in a stable condition on arrival.

According to Fonterra's website, Clandeboye is one of its largest sites and processes up to 13.2 million litres of milk per day.

"This equates to more than 40 per cent of all milk collected by Fonterra in the South Island, making the site home to New Zealand's largest liquid load carrying fleet of trucks," the website said.


In August, Fonterra wrongly suspected that 38 tonnes of whey protein - used to make a range of products including infant formula manufactured by Nutricia - had been contaminated with a botulism-causing bacterium.

Dairy products, including infant formula, were withdrawn in more than seven countries as a result of the scare.