UPDATE 5.45PM: Police have confirmed that five people have died after a bus carrying 23 Chinese tourists rolled on State Highway 5, just outside of the Bay of Plenty.

The accident occurred near Waiohotu Road and Galaxy Road, Mamaku at 11.20am.

A number of people were taken to hospitals in Hamilton, Rotorua and Tauranga.

Police say the bus was travelling south and failed to take a ‘moderate to easy' bend, crossed toward the other side of the road, corrected, then flipped onto the driver's side. The driver was not seriously injured.

They described the road as reasonable hilly, with the weather at the time very ‘unfavourable', with high winds and rain.

Police say the road would be closed until late Wednesday evening.

-Additional reporting from Stuff.co.nz

Bus crash SH 5, Ngatira update: 1 serious and 1 moderate to Waikato by air, 1 serious to Tauranga by air, 3 moderate to Rotorua by road. 15 patients transported to secondary triage area for further assessment.

— St John (@StJohnAlerts) September 4, 2019

EARLIER:

A number of people are dead following a bus crash just outside of the Bay of Plenty.

Emergency services are continuing to work at the scene of the serious crash on State Highway 5, near Mamaku, about 20 minutes north of Rotorua, where a bus has rolled.

It is believed more than 20 people were on board the bus at the time of the crash, says a police spokesperson.

'A number of those passengers are reported to have been injured.

'Patients are being transported to both Waikato and Rotorua.

'Police can advise there have been fatalities in the crash, however the number cannot yet be confirmed.”

The Serious Crash Unit and the Commercial Vehicle Safety Team are attending the scene alongside other Police staff.

The road is expected to remain closed for some time, and motorists are asked to avoid the area and delay travel.

EARLIER:

Emergency services are responding to reports of a serious crash on State Highway 5, Ngatira, north of Rotorua, where a bus has rolled.

Information on any injuries is not yet available, says a police spokesperson.

"The road is closed, and diversions will be in place.

"Motorists are advised to avoid the area."

In a tweeted alert, St John says they have dispatched five helicopters, three ambulances and a manager to the scene.

"We are assessing patients and will update any information as it comes to hand."

SH5 NGATIRA - SERIOUS CRASH - 11:55AM
A serious crash will shortly close #SH5 between Tirau and Ngongotaha (Rotorua). Long detours via Tauranga or Tokoroa will be required. Delay your journey or allow extra time: https://t.co/FQaOg3vnET ^TP pic.twitter.com/DWhnVIPMrO

— NZTA Waikato/BoP (@NZTAWaiBoP) September 4, 2019

Traffic travelling along the route is being turned back into Rotorua as police cordon off the road approximately half a kilometre away from the crash.

The crash occurred in overcast conditions and heavy rain.A police officer directing traffic back said the road would likely be closed for a number of hours.

NZTA said diversions will be in place between Tīrau and Ngongotaha. Long detours via Tauranga or Tokoroa would be required, they said.

Motorists are advised to avoid the area.

A woman from Rotorua, who preferred to remain anonymous, said she had never seen so many emergency services travelling on Ngongotaha Road near Rotorua.

She estimated at least 15 vehicles, which included ambulances, firefighters and volunteer services.

It was "really bad" and it was "the most we have ever seen go to a callout"," she said.

Mel Moon, who lives near Waiohotu Road, said the highway was a busy road which tourist buses often used.

However, she didn't know anything about the circumstances of Wednesday's crash.

Locals described the weather as pretty windy, and off and on heavy rain.

More as it comes.

-Additional reporting by Stuff.co.nz