A gas production facility in South Taranaki is temporarily shut down after high levels of vapour were vented from a storage tank.
Ambulance officers were called to the Kapuni production station shortly before 10.30am on Monday and treated one person who was overcome by fumes.
The Fire Service sent four engines and a specialist hazardous chemical unit.
Shell Todd Oil Services says all personnel are accounted for and unharmed, and there has been no damage to the facility.
It says the plant remains shut down until the cause of the vapour venting has been determined.