Te Araroa and Tikitiki firefighters responded, along with police. St John Ambulance from Ruatoria was also called out.
St John Ambulance officers pronounced the victims dead at the scene.
The state highway was blocked immediately after the crash and remained closed to all traffic for some hours.
The police Serious Crash Unit from Gisborne was called to the scene to start an investigation.
"This was a single-vehicle crash," a police spokesman said.
"We had the road open to one lane for a while but due to the number of 'rubberneckers' coming to have a look we had to shut it down completely."
He indicated the Coast highway would remain closed possibly until mid-afternoon at the earliest.
Waka Kotahi New Zealand Transport Agency asked motorists to take extra care and expect delays at the crash site.