Two people have died and two more are seriously hurt in a crash near Dunedin. Three rescue helicopters helped treat the injured.
A fifth person suffered moderate injuries.
Emergency teams rushed to the two-car crash on State Highway 1, south of Waihola, about 9.15am - as a top cop urged Kiwis to stay safe on the roads this long weekend.
Three people were treated at the scene, it said.
St John earlier said two critically injured patients were flown to hospital in separate helicopters, and a third was taken in by road.
SH1 is currently closed and diversions are in place, police said.
"Northbound traffic is being diverted along Phosphate Rd, and southbound traffic is being diverted through Taieri Mouth," police said.
Police said the diversion route is not suitable for trucks and heavy vehicles and these should expect lengthy delays.
The Serious Crash Unit has also been advised.
A Fire and Emergency New Zealand shift manager said four of its crews attended.
Two other people have already died in crashes during this long weekend.
A woman was killed when hit by a truck at Ōtāne in Central Hawke's Bay late yesterday afternoon, and a motorbike rider died in a crash with a car on State Highway 1 in Burnham, near Christchurch.
Road policing director Steve Greally said each death is a tragic loss.
"It's a person who should have had a future, they have family and friends, but unfortunately because of a mistake - whether it was them or somebody else - they're no longer with us, and the effects of that with their families [is] huge and everlasting," he said.
Greally urged drivers to follow basic road safety rules.
This included making sure that drivers are not impaired by alcohol, fatigue or drugs, making sure that people aren't distracted by their cell phones, he said.
"And of course making sure that people drive to the speed that's suitable - not only for the weather conditions, but also for the type of road, and no [faster] than the speed limit."