Police have confirmed five of the 27 passengers aboard the bus have died after a serious crash on State Highway 5 in Ngātira near Rotorua.

Photo: Bishal Jung Basnet / Supplied

Inspector Brent Crowe said it was reported that a bus rolled in Ngātira, west of Rotorua, at about 11am.

"Two people were seriously injured, further four received moderate injuries, and the remainder of those persons on board the bus were either injured to a lesser extent or were able to walk away from the scene."

Photo: Bishal Jung Basnet / Supplied

He said the tour bus was carrying Chinese nationals.

An investigation has commenced. Police were working with the Ministry of Foreign Affairs and Trade and the Chinese Consulate to identify and find the next of kin of those killed.

The serious crash unit and the commercial vehicle safety team are still at the scene.

State Highway 5 has reopened between SH38 (Tapapa) and Maraeroa this evening after being closed following the crash.

Mr Crowe said the bus was travelling south towards Rotorua and rolled over a moderate-to-easy bend.

No other vehicles were involved and the driver was not seriously injured.

He said it was too early to tell if charges would be laid.

Chinese ambassador Wu Xi has gone to Rotorua to meet those involved in the accident.

Liang Zhi from the Chinese Embassy said Ms Xi would be talking to the authorities and survivors.

"Our ambassador is on her way to Rotorua to help with the handling of the accident. I think she will meet with the local police authority and government officials and also to meet with the people injured in the accident."

6:45PM FINAL UPDATE

SH5 has fully REOPENED between SH28 (Tapapa) and Maraeroa Rd following a crash this morning. Please continue to drive with care in the area. Thank you for your patience today. ^MF https://t.co/bn93sDtTfO — NZTA Waikato/BoP (@NZTAWaiBoP) September 4, 2019

Five helicopters, three ambulances and a St John manager were sent to the scene.

Photo: NZME / Ben Fraser

St John said one patient in a serious condition and another in a moderate condition had been airlifted to Waikato Hospital.

Waikato Hospital staff with Mandarin language skills had helped with translating.

Another person in a moderate condition was airlifted to Tauranga Hospital.

Three patients in moderate to minor condition were taken by Rotorua Hospital and 15 patients are being assessed.

NZME reports that a police officer said they arrived at the site and found "people everywhere".

A police officer told reporters at the scene: "It is a major crash, we've got people everywhere, you can't come any closer at the moment."

Survivors have emerged from the crash site wrapped in blankets.

A spokeswoman for an Auckland-based international travel company said they had been contacted about a crash near Rotorua this morning.

"We received reports from our driver. At the moment we don't know the extent of things and we are busy trying to sort things out."

Photo: NZME / Ben Fraser

A spokeswoman from Kuranui Wilderness Lodge and Trophy Park said the crash was east of its premises and she had seen multiple police and ambulance vehicles going past and two helicopters in the air.

The police serious crash unit and the commercial vehicle safety team remain in the area. The road was closed and motorists had been asked to avoid the area. The Transport Agency said long detours via Tauranga or Tokoroa would be required.

A reporter at the scene said traffic was backed up for hundreds of metres and drivers were being asked to turn around.

There had been persistent rain throughout the morning at the site, which is a 20-minute drive from Rotorua and there are patches of light surface flooding on the road.

Photo: RNZ / Andrew McRae

However, a Ngātira resident said it was a tragic freak accident because the road wasn't dangerous otherwise.

Carol Sklenars drives State Highway 5 toward Mamaku four times a day to take and pick up her children from school.

She said the road wasn't dangerous or difficult and the weather today wasn't particularly bad.

- RNZ with NZME