It's feared 2500 children who visited a dental clinic in south Auckland could have been exposed to viral infections including hepatitis and HIV.
It was discovered late last week that equipment at Pukekohe Intermediate Dental Clinic was not functioning correctly.
Those who attended the clinic between September 13 and January 23 could be at risk and will be screened, according to Counties Manukau Health.
Hepatitis B, Hepatitis C and HIV testing will be offered to children who had a procedure involving compressed air, a drill, extraction or suction.
"It is critical for parents to understand the risk is very low. If we do find cases of pre-existing infection, then we will prioritise screening for those children who were treated on the same day," says Dr Gloria Johnson, Counties Manukau Health's chief medical officer.
Counties Manukau Health says the Pukekohe Intermediate Dental Clinic was the only one affected.
"An investigation is underway into the exact nature of the problem and how it occurred," Counties Manukau Health said.
Concerned parents should call Healthline on 0800 611 116 or contact their GP.