One person is dead and 14 others are injured after a small bus loaded with international tourists collided with two vehicles on a straight stretch of State Highway 1, north of Tīrau, on Wednesday afternoon.

Hato Hone St John says it sent 13 vehicles to respond to the accident and took 13 patients - two in critical condition and four in serious condition - to Waikato, Rotorua, Tauranga and Auckland hospitals by road and air.

The highway was closed for several hours for more than 10km, between Tīrau and Piarere roundabout, but has since reopened.

Emergency services were called to the scene just after 2pm, where the wreckage of a Mazda ute, sedan car and the small bus towing a trailer now remain.

Hato Hone St John sent four ambulances, two rapid response units and five helicopters to retrieve the injured.

Taupō road policing manager Senior Sergeant Fane Troy said there were 11 tourists and their driver in the mini-van, and three others in the two other vehicles.

Hato Hone St John sent four ambulances, two rapid response units and five helicopters to retrieve the injured. Photo: Auckland Rescue Helicopter Trust

He said one person died and the 14 others involved were injured. Initial indications were that some suffered serious injuries.

It was not clear yet where the tourists were from, but Troy said they were from outside New Zealand.

He said it was too early to establish the cause of the crash or release details regarding the deceased.

When RNZ arrived at the scene, near the intersection with Paparamu Rd, crash debris littered the highway.

The sedan remained covered and it was understood family members were waiting nearby.

The scene of a crash on SH1, north of Tīrau. Photo: RNZ / Natalie Akoorie

Troy said the emergency response was extensive due to the number of injuries.

"Police just want to reiterate to all road users around taking time when they drive. Be safe, be courteous on the roads."

He said this part of Piarere where the crash happened was not usually a blackspot.

"Crashes can happen anywhere and it can be for a number of different reasons but it's not a typical crash spot for us."

He estimated the road between State Highway 29 and SH27 would be closed for at least four hours and advised motorists to avoid the area if possible.

Troy said a scene examination was now underway and police had put a drone up.

He apologised to motorists for the road closures, but said it was a necessary consequence of a serious crash.

"Unfortunately it's becoming far too often we have to attend these things with all emergency services. We'll look after our staff, we've got support services around for that.

"Our thoughts do go out to those people affected by this."

-RNZ