Fire chief Gavin Gibbens said the crash occurred on a straight piece of road.
St John acting territory manager Emma Kay said staff from Greymouth and a first responder from Punakaiki also attended.
The seriously injured man was airlifted to Grey Base Hospital.
Police are undertaking local inquiries into what happened, in conjunction with an ongoing investigation by the serious crash unit.
"We believe that speed was possibly a factor in the crash, however our investigation will carry on with local inquiries," senior sergeant Paul Watson, of Greymouth, said.
Meanwhile, a 28-year-old man had a brush with death when his car plunged down a bank above the Grey River near the Brunner Mine site, north of Taylorville.
His car came to rest against a tree, about 30m below the Taylorville-Blackball Road and just above the river, about midnight on Saturday.
The Greymouth Volunteer Fire Brigade was called about 12.30am.
The driver "was lucky" the car did not fall any further, fire chief Lee Swinburn his car left the road.
"The vehicle came to a stop against a tree," Watson said.
The driver was moderately injured, with a fractured nose, "possibly due to not wearing a seatbelt".
Watson said the man had submitted to a blood-alcohol test for suspected drink-driving.
- Greymouth Star
