A Fire and Emergency New Zealand (Fenz) statement said three fire trucks, three support vehicles and a senior officer are in attendance.
SH1 is closed and diversions are in place for both north and south-bound traffic.
“Motorists are advised to avoid the area and use an alternative route where possible,” police said.
A Hato Hone St John statement said they were in attendance but police were the lead agency.
“Avoid the area, use alternative routes where possible and expect delays,” New Zealand Transport Agency Waka Kotahi said on social media.
It comes after two people died and a third was moderately injured in a crash on the same stretch of road earlier this month.
Emergency services responded to a pile-up on Main North Rd/State Highway 1, near Sefton, shortly after 10am on January 8.
Police Senior Sergeant Stephen McDaniel confirmed the earlier double-fatal collision was between two cars.
“It appears that one vehicle left the side of the road and collided with another coming from the opposite direction”.
“We do not know the cause, but we know that one vehicle has crossed the centre line, hitting the other. We are still ascertaining the cause of the collision,” McDaniel said the day after the crash.
Images from the crash scene showed debris from a flipped silver Hilux ute strewn across the road and a host of emergency workers at the crash site. A silver Corolla was off the road, in bushes, and had been covered with a sheet.
Meanwhile, emergency services were also responding today to a serious single-vehicle crash that closed the Otira Highway, SH73, on the South Island’s West Coast.
The crash in Jacksons, Westland was reported about 3.40pm.
“Initial indications suggest there are serious injuries,” police said.
Earlier today, one person was critically injured and part of Hawke’s Bay’s main highway, SH2, was closed for more than five hours after a crash involving a motorbike and a car.
A man was flown to Wellington Hospital after the crash near Te Hauke, between Hastings and Waipawa, was reported to emergency services at 9.27am.
No other injuries were reported.
Police announced after 3pm the section of road had re-opened after a police Serious Crash Unit investigation at the scene near the highway’s intersection with Colin White Road.