There were no available local road detours and State Highway 5 was closed between Napier and Taupō, it said. Drivers were advised to avoid the area or delay their travel.
A Hato Hone St John spokesperson said two ambulances and a helicopter were dispatched, while fire and rescue crews from Napier and Taupo also attended.
No further detail about the injured had been released by 5pm.
Napier traveller Karen Crawley, who was on her way from to Hawke’s Bay from Ruapehu and was trapped in the queue west of the crash site since before the arrival of the first emergency services, said: “It’s wet and miserable and my heart goes out to all those involved.”
“The visibility is very poor, and if it wasn’t raining it would be nice to get out and stretch,” she said.
Other motorists said fog had caused problems with visibility on the highway earlier in the morning.
As torrential rain fell early in the afternoon Crawley said most southbound cars appeared to have turned back towards Taupō, and the queue was mainly trucks.
The speed limit of 80km/h, installed on the highway three years ago, reverts to 100km/h at 6am on Thursday.
Emergency services on Wednesday afternoon also went to another collision involving a truck in Napier about midday. The second vehicle in the crash at the intersection of Niven and Wakefield streets, in the Onekawa Industrial District, was a ute. Police said soon afterwards there were no injuries.
