Brave locals rescued three children from the wreckage of a helicopter crash before a farmer pulled the mangled aircraft out of the mouth of the Kekerengu River.
Two people were killed in the crash and three others - the children - were seriously injured before they were later airlifted separately to Wellington Hospital.
Two adults are reportedly feared dead with the children surviving the crash.
Investigators will comb through the wreckage tomorrow morning as they work to understand the circumstances that led to the crash.
The Transport Accident Investigation Commission has opened an inquiry and tonight appealed for witnesses – "especially anyone who may have captured the accident on their vehicle's dash-cam or other recording device - to please contact TAIC as soon as possible."
They have set up a perimeter around the wreckage prohibiting public access in order to protect evidence.
Fire and Emergency New Zealand (Fenz) operational insurance team member Darryl Papesch believed those rescued were children.
He was one of the first responders on the scene after visiting the local volunteer fire brigade and said locals had pulled everyone out of the wreck by the time he arrived.
The tractor owner told TVNZ: "We all just heard a bang as it hit the ground and all the locals rushed out and rallied around with blankets and that sort of thing, and we managed to get some of the people out of the helicopter."
He grabbed his tractor and pulled the helicopter away from the water's edge "out of harms way".
He said locals "without a doubt" managed to save lives with their quick actions.
"There was a lot of us who did what we could. The local nurse heard about it and came rushing down. I call it a team effort."
The crash took place outside The Store, a popular spot for heli-tourists to visit, in the small town located around 30-kilometres north of Kaikōura, at 12.42pm.
The helicopter was an Airbus Helicopter EC120 and is came from Christchurch.
Mehrtens wife, Coastal Lodge owner Lyn Mehrtens also watched as the chopper plunged to the ground, spinning in circles as it descended.
"We just watched it go round and round and round," said Mehrtens.
"It's scary. You're just so helpless. You can't do anything."
Papesch believed the helicopter was partially in the surf of the Pacific Ocean coast.
Harald Hendel, TAIC's chief investigator of accidents, says there may be people who saw what happened, given the location of the accident adjacent to a busy café on State Highway 1.
He has appointed an investigation team and they are scheduled to be on site tomorrow morning.
"The Investigation team have expert knowledge of helicopter operations, engineering and maintenance.
"Their initial work will include inspecting the wreckage, mapping the site, and talking with witnesses. Further evidence gathering in coming weeks and months will likely include examining the helicopter's components, seeking any recorded data from the helicopter's electronics, and obtaining maintenance records."
Rescue helicopters were sent from Christchurch, Nelson Marlborough, and Wellington, and a commercial helicopter was sent from Kaikōura.
Each of the rescue helicopters then flew a patient each to Wellington Hospital, said Simon Duncan, general manager of GCH Aviation which operates rescue helicopters and air ambulance services.
A spokesperson for the Capital and Coast District Health Board said the three patients were being assessed in the emergency department.
"All three rescue helicopters from around the region were sent to the scene not knowing what they are going to come across," he said.