An Australian traveller says poor conditions made for a scary drive over the road where two buses rolled on State Highway 8 in the Mackenzie District this morning.

Fifteen people have been taken to hospital by St John after the single-vehicle crashes occurred 100 metres apart on the Tekapo-Twizel Highway about 8.40am on Thursday, police said.

That includes seven from the scene of the crash, including two people in a serious condition, two in a moderate condition and three with minor injuries.

Eight were transported from Twizel Medical Centre, six in a moderate condition and two on a minor condition.

Hato Hone St John earlier said it was notified of the incidents at 8.38am and nine vehicles and three helicopters had been dispatched.

The two seriously injured had been taken to Dunedin and Timaru hospitals via helicopter.

Grace, who was travelling along the road when she came upon the scene, said she gave first aid to visibly shaken passengers.

"The children were quite lacerated by the glass I believe," Grace said.

She spent 25 minutes tending to wounds and trying to keep people warm on a bitterly cold morning before the firefighter crews arrived.

A bus crash involved tourists on State Highway 8 in the Mackenzie District on 18 July, 2024. Photo: Supplied / Grace Duggin

A man had helped to get all the passengers out of the first bus before she arrived.

"But as the temperature was about negative one (degrees), they were just freezing, so everyone was gathering all the blankets and scarves and jumpers that they could to give to these people," Grace said.

The driver appeared to be in shock with a broken arm or wrist, and the children were upset and crying, she said.

She was driving to Christchurch with friends when they pulled over after seeing cars with their hazard lights on.

"We were super scared on the road ourselves cos of the black ice and really poor conditions, so I think something really needs to be done about that."

She felt shocked to not to find more road safety signs and information along the highway.

"Considering it's a 100 [kilometre an hour] zone, we were going about 30 so I think that it's just not at all well equipped, especially for vulnerable tourists who aren't familiar with the conditions."

She wanted to see action so travellers were better informed about the road conditions and the highway was better maintained and able to cope with the conditions.

Police said it was understood those on board were international tourists, and the relevant Consulate had been advised.

A Chinese Embassy spokesperson said staff from the Christchurch Consulate was on the way to the scene.

In a statement, a spokesperson at the China Consulate-General in Christchurch said they were advised by police that two buses were carrying Chinese tourists had rolled.

Staff from the consulate had visited the seriously injured pair and the embassy had asked travel agencies to accommodate the remainder of Chinese tourists involved, the spokesperson said.

"Our consulate once again reminds Chinese citizens who are recently visiting the South Island of New Zealand: the weather in the South Island is changeable in winter, with rain and fog and the slippery roads and "black ice" from time to time.

"Please be sure to stay cautious on the road, drive slowly and wear a seat belt."

Some of those injured were taken to Twizel Medical Centre. Photo: RNZ / Niva Chittock

Passengers on board the buses who have not required medical attention have been taken to Twizel.

Earlier, about 40 firefighters from four crews around Twizel, Lake Tekapo, Omarama and Otematata were at the scene.

Fire and Emergency (FENZ) said no one was believed to be trapped after the crashes.

The road is closed between Tekapo and the intersection with State Highway 30.

The New Zealand Transport Agency / Waka Kotahi (NZTA) advised motorists to expect delays, with this section of the road possibly staying closed for the rest of the day and no immediate detours available.

"Drivers should allow at least two hours longer for travel times while SH8 remains closed.

"Westbound travellers should use SH8 east to Timaru, SH1 south to the SH82 junction, and the inland route on SH82 to Kurow/SH83 junction, with westbound to SH8/83 Otematata. Eastbound travellers should use the reverse route."

"Weather conditions were foggy at the time, however the exact cause of the crashes is still being determined," police said.

A FENZ shift manager said crews were faced with poor weather, fog, ice and multiple patients.

"Crews worked extremely hard in trying conditions to get the best outcome for the public," he said.

Fire and Emergency crews left the scene about midday, but the road remained closed.

NZTA said as this was a serious crash on a state highway, they would be conducting an investigation of the road and roadside conditions, alongside police investigations.

"The condition of both buses will also be examined as part of the investigation.

"Our thoughts are with everyone affected by this morning's crash."

Intersection near bus crashes popular with tourists - board member

Twizel Community Board member Tracey Gunn said conditions in the area could be treacherous, making locals wary.

She said she was not surprised to hear about the two bus crashes near the Hayman Road intersection, which was popular with tourists as it had a car park with toilets and breathtaking views.

"Close to the lake and with the fog, the roads are wet. Sub-zero temperatures means they freeze, black ice, and you can't see black ice. It just looks like a wet road," Gunn said.

"It's just a perfect storm of conditions for accidents unfortunately."

On Thursday morning, NZTA put out a black ice and winter driving conditions warning for that stretch of road.

Gunn said it was one of the two intersections in the area which had the most crashes, because it was a sweeping bend which was a bit tricky to go through even in good conditions.

"If the visibility is very low and so if you're driving down the main road, you wouldn't even know that there was potentially an intersection there."

Under winter conditions, motorists needed to go slower, brake on a straight, not on a corner and factor in more travel time, she said.