The Fire Service has been called to an unnamed incident at Rio Tinto's Tiwai smelter in New Zealand.
Two decontamination sites have been set up, one at the Tiwai Wharf and the other at the nearby Southland Hospital, according to Fairfax NZ.
Four people have reportedly been taken to hospital although they had to be decontaminated prior to entry, while another 11 were decontaminated at the wharf and take to hospital as a precaution.
A spokesperson for the Rio Tinto owned New Zealand Aluminium Smelters has confirmed that an incident has occurred, but declined to say what the event was, only stating that more information will be released soon.
The workers were reportedly exposed to pitch fumes.
The incident occured while workers were loading metal onto a ship, and the vessel's pitch tank system vented.
Fairfax NZ says all members of the loadout team, which included seven stevedores, five truck drivers, and four other smelter workers, were taken to hospital.
They have all since been released from hospital.