Police have named the three people who died in a crash on Whananaki North Rd, near Whangārei, early on Sunday morning.
Maurice Kareko, 35, Rhiannon Walters, 11, and Alec Walters, 5, died after a car crashed into a tree at around 2.15am.
Another child remains in Whangārei Hospital in a serious condition, while a fifth occupant of the vehicle received minor injuries.
The road was closed overnight while emergency services conducted a scene examination.
Police haven't been able to confirm what caused the incident and investigations are ongoing.
The crash came after Northland police posted on their Facebook page on Saturday warning of a high crash risk.
"Take extra care on Northland roads today. After a long dry spell there may be oil, fuel and other contaminates on the road surfaces. These will become slippery when mixed with water," the post said.