Forty-seven people were on the crater when it erupted on December 9. Twenty-two people later died after suffering extreme burns and blast injuries, including 14 from Australia.
A case review hearing was held in Whakatane District Court on Thursday morning with Judge Evangelos Thomas.
New Zealand's workplace safety watchdog said all but one of the dead were involved with White Island Tours: 19 were customers, visiting from Tauranga-docked cruise ship Ovation of the Seas, and two employees.
"The significance of these pleas can't be understated," WorkSafe chief executive Phil Parkes said today.
"The survivors and the families of those tourists and workers who died or were seriously harmed will carry this impact for the rest of their lives.
"We hope the decision of White Island Tours will provide some assurance to the survivors and family... of those who passed that those who had a duty to ensure their safety and failed to do so are being held to account."
Of 25 other people who were injured in the eruption, 21 were on the island through White Island Tours.
White Island Tours Ltd was charged under Section 36(1)(a), 36(2), 48(1) and (48)(2)(c) of the Health and Safety at Work Act 2015.
- Failing to comply with a duty to ensure the health and safety of workers so far as is reasonably practicable.
- Failing to comply with a duty to ensure the health and safety of other persons so far as is reasonably practicable.
In a statement to media, White Island Tours director Paul Quinn said the company "deeply regretted" its role in the tragedy.
"The company's risk assessment processes did not adequately identify the risk of a significant eruption taking place without warning on Whakaari, therefore creating a risk to visitors and employee," he said.
The charges relate to safety measures in the lead-up to the eruption, and carry a maximum penalty of $1.5 million.
The deadly blast produced the country's largest and most expensive workplace safety investigation, in which WorkSafe brought charges against 13 individuals or organisations.
Legal complexities have delayed a trial until next month, when proceedings expected to last four months will begin in the Auckland District Court.
White Island Tours will be sentenced after the trial.
In 2022, Auckland-based scenic flight operator Inflite also pleaded guilty, ordered to pay $267,500 in fines and costs.
Two other government organisations, the National Emergency Management Agency and research institute GNS Science, had charges dropped last year.
GNS Science also pleaded guilty to one of its charges.
The charges against GNS related to multiple field trips its staff took to the island before the eruption and the institute's failure in its duty to the helicopter pilots, who were contractors.
Last month Andrew, James and Peter Buttle - the owners of the volcanic island - failed to have their charges dropped.
Nine defendants will now go to trial, including island's owners.
- additional reporting RNZ
