WorkSafe says it could take up to 12 months to investigate an accident in Rotorua in which a woman fell into a sinkhole and suffered severe burns.
It has opened a formal investigation into the incident.
The woman, from Perth, Australia, is in a serious but stable condition at Waikato Hospital.
The geothermal sinkhole which was about two meters long and one meter wide and long has been backfilled and steam grates installed.
The woman entered Whakarewarewa Village last Thursday afternoon when the ground fell away.
The sinkhole was deep and steam-filled, and a volcanologist said heavy rain may have contributed to the collapse.
The village is temporarily closed.