"While we don't know the exact cause and source of this illness, we now believe it is botulism," a Waikato Hospital spokeswoman told

NZ Herald

on Friday.

"The three patients are responding to botulism anti-toxin and are recovering in hospital.

"We have sent samples off to a specialist centre in Queensland for testing but it may take several weeks before we get the results. We have no evidence to believe there is any public health issue."