Three people are in Waikato Hospital after a bus crashed in Tongariro National Park.
The vehicle rolled half way up Ohakune Mountain Rd, which runs to Turoa skifield.
Police were alerted just after 2.30pm.
They have confirmed that 31 people were onboard the bus.
Helicopters were called in to assist, police said, and three people were flown to Waikato Hospital - a woman is in a critical condition, another woman is stable and a man is in a serious but stable condition.
Other passengers had been taken to the ambulance station in Ohakune for assessment.
A salvage team would work to remove the bus.
In a Facebook post, the ski operator said Turoa would be shut on Sunday.
"Due to the serious nature of this incident we will take the opportunity to undertake a detailed debrief and review to verify the safety of our bus fleet before we reopen Turoa on Monday."
Whakapapa would continue to operate as normal.
RNZ reporter Gia Garrick, who was at the ski field, said she had to wait with a few hundred people at the ski field cafe for several hours until the road reopened.
The weather was bad at Turoa all day, she said, and the visibility was so poor she could only see about 20 metres in front of her.