Fifteen people were injured - four seriously - but the outcome of a dramatic Central North Island bus crash could have been much worse, a firefighter at the scene in Tongariro National Park says.

A major rescue operation involving dozens of ambulance, fire, police, rescue helicopter and air ambulance staff was launched after the bus carrying 15 British and American tourists crashed down 10m bank and into a stream just after 8am.

St John Ambulance confirmed four seriously injured people, including a woman initially trapped partially submerged in water following the crash at the intersection of State Highways 47 and 48, were flown to Waikato Hospital.

Eleven others with a range of minor to moderate injuries were taken by ambulance or bus to Taupo, Rotorua and Whanganui hospitals. Those on the bus are believed to be in their 60s.


About 9.30pm, a spokesman for Whanganui Hospital said they had five patients with them - all of whom were in a stable condition.

A spokeswoman for Waikato Hospital said they had two patients with them. Both had suffered serious injuries, but were in a stable condition and were in a ward.

National Park Volunteer Fire Brigade chief fire officer Neil Ranford was among more than two dozen firefighters sent to help.

The bus was travelling west along SH48 - the access road to Whakapapa and
Mt Ruapehu - when it appeared to have crossed the T intersection with SH47 and plummeted down the bank, Ranford said.

Fortunately, no vehicles were travelling through the intersection at the same time, Ranford said.

"They were very lucky ... there's been a couple of fatalities on that corner."

The bus ended up on its side in the stream, but the water level was less than a foot high, he said.

Cutting equipment was used to free the partially submerged woman, and she, along with several other passengers, was stretchered up the bank to waiting ambulances.

A rope line was set up to help other passengers, all believed to be aged in their 60s, climb up the bank, Ranford said.

Little was said.

"They were all knocked around a bit from going down that bank ... they were all looking a bit shocked."

Weather conditions were very misty, but it was not too cold, he said.

St John Ambulance district operations' manager Steve Yanko said five ambulances and a operations' manager were sent, and three rescue helicopters flew to a staging post five minutes drive away.

Rain and low cloud prevented the helicopters from landing at the site.

Chateau Tongariro general manager Kathy Guy said those involved in the crash were guests.

The company of a tour bus that crashed - injuring fifteen tourists - has apologised and says its main focus now is helping passengers and staff involved in the accident.

Tour operator Moa Trek released a statement this afternoon, acknowledging one of its buses had crashed at the Tongariro National Park this morning.

The accident happened just after 8am.

Company director Miles Clark said he and members of staff were on their way to see the passengers to provide whatever support the company can offer.

"We are very sorry that this has occurred on one of our tours and we are working hard to ensure we do whatever we can to support our team member (driver) and our passengers,'' he said.

"Beyond that, we will work with our industry colleagues to support, accommodate and revise travel arrangements as necessary for all those affected."

The company said it will be co-operating fully with authorities carrying out an investigation into the accident.

It also praised the efforts of people - including emergency services - who were first at the scene of the crash.

Clark said: "The immediate priority is the health and welfare of those injured and needing the most attention.''

The national park is popular with tourists, especially those wanting to walk the Tongariro Alpine Crossing.

Tour operators have cancelled their operations on the crossing today due to 90km/h winds and 40mm rain.

The serious crash unit is investigating the cause of the crash.