A van that plunged down a cliff and onto railway tracks in the central South Island yesterday, killing a woman and injuring five others, did not have any back seats, investigators say.
The incident could have caused a major disaster as a train was just minutes away when the vehicle landed on the tracks.
It left State Highway 73 between Cass and Bealey Spur, south of Arthurs Pass, in thick fog about 6am and rolled up to 60m down a steep bluff.
A source connected to the investigation, who did not want to be identified, said the van did not have any back seats.
The woman who died was thrown from the vehicle, the source said.
"It's always dodgy driving with nobody strapped in. But we haven't determined whether a lack of seatbelts was a major cause yet."
Police were awaiting the results of toxicology tests to see whether alcohol was involved, and also whether fatigue was a factor.
A train had been scheduled to pass through the area within minutes of the crash.
"There's trains scheduled to pass through that area all the time. In the time we were there we had to hold up four or five of them.
"Had it been cleaned up by a train it could have been [a major disaster]. That's the main rail feed to the West Coast so it's a busy line."
A KiwiRail spokeswoman said yesterday that about 130 passengers travelling from Christchurch to Greymouth had to be transferred onto buses as a result of the crash.
Barrie Drummond, a former railway worker who lives 4km from the crash site, arrived there about 7.30am. He said the vehicle was "squashed like a tin can".
"It couldn't have been a worse morning for fog and it was lucky that a coal train coming from Westport was stopped about 10km from Arthurs Pass or it would have been a terrible disaster," Mr Drummond told the Herald on Sunday.
He was told the driver had somehow scrambled up the bank through the bush and managed to stop a passing milk tanker to help.
"I believe that the woman who died was found in the river that runs alongside the railway lines," Mr Drummond said.
Five other people in the van were injured, two critically, and three helicopters were dispatched to fly them to hospital.
It was the second fatal crash on the same South Island alpine highway yesterday.
The other occurred near Porters Pass in the foothills of the Southern Alps about 5.30pm. A 39-year-old Christchurch woman was killed when her station wagon and a tour bus collided about 5.30pm.
St John Ambulance said the bus driver also received minor to moderate injuries.
Senior Constable David Pitkethley said weather and road conditions were fine and it was unclear what had caused the crash.
"The things we look at are the vehicles and the scene and try to establish whether there's any one factor that's contributed to the accident," he said.
- additional reporting: Russell Blackstock and John Weekes of the Herald on Sunday