A ute may have been driven dangerously on a Northland beach before the horrific crash which claimed the lives of three Brethren church members, police say.
The crash in Northland on Monday brought the Queen's Birthday weekend road toll to 11 - the highest in 27 years.
Susie Stewart, 48, her daughter Sadie, 16, and family friend Jamie Wearmouth, 18, died when a ute hit a tree on Baylys Coast Rd near Dargaville about 6.40pm.
Mrs Stewart and the two teenagers were members of the Plymouth Brethren church, previously known as the Exclusive Brethren.
The group had been travelling home from Baylys Beach when the crash happened.
Police are calling for witnesses as their serious crash investigation continue.
Northland road policing manager Inspector Wayne Ewers said police were interested in talking to anyone who saw the dark blue Mitsubishi Triton on the beach.
"We have information suggesting the ute may have been driving dangerously on Baylys Beach prior to the crash, and passengers were seen riding in the back tray of the ute on the beach," he said.
Police were also interested in hearing from anyone who may have witnessed the crash or who may have stopped to help injured passengers, Mr Ewers said.
"We're also keen to hear from anyone who may have seen a person walking from the scene of the crash."
Eight people, including the three dead, were travelling home from the beach when the ute left the road on a right hand bend and hit a large tree.
Three were seriously injured, while the driver and a female rear-seat passenger received minor injuries.
Two males on the tray were thrown from the vehicle when it hit the tree, landing a short distance away. Both were taken to Whangarei Hospital with non-life threatening injuries.
Police have asked for anyone with information to contact Constable Reuben Cohen at Dargaville police on 09 439 3400 or Crimestoppers, anonymously, on 0800 555 111.