It is likely a landslide in the Haast Pass hurled the campervan that missing Canadian tourists Connor Hayes and Joanna Lam were travelling in last Tuesday into the raging and flooded Haast River.
At a media conference this afternoon West Coast police area commander Inspector John Canning said police believe the couple's vehicle was hit by a landslide.
The couple were travelling from Haast towards Wanaka. The accident happened sometime after 6.30pm, he said.
"We know roughly when it happened as we have spoken to a witness from Haast who was following a campervan through the Haast Pass last Tuesday and turned back because the weather was so bad.
"Unfortunately there is no sign of the couple, but we will continue searching - things are not looking good for their survival,'' he said.
Mr Canning said he would be talking to the Coroner because there had been no signs of the couple which "indicated they may have come to harm''.
Mr Canning also said that searchers scouring the river in a jetboat today told him that the water was 6m higher last week during the terrible weather than what it was today.
Ms Lam's brother Jeffery listened into the the media conference from Canada via telephone afterwards thanked all the searchers for their efforts.
"Also on behalf of our family and friends I hope and pray you find something which would be able to give our families closure,'' Mr Lam said.
Hopes are fading for the missing tourists after more wreckage of their smashed up campervan from the Haast Pass was found 50km away, washed up on the beach.
The fuel tank was found last night north of the Haast River, near the Waita River.
A search was launched yesterday morning when Mr Hayes, 25 and Ms Lam, 24, were reported missing after Ms Lam failed to turn up to her first day of work at the radiology department at Nelson Hospital.
The couple were last seen at Fox Glacier last Tuesday afternoon; the day the weather bomb exploded over the region; lashing the Haast Pass alpine area with torrential rain and gale force winds.
Haast police Constable Rob Manera discovered the chassis and wheels of the campervan in the narrow gorge, just metres from the landslide at Diana Falls.
West Coast police area commander Inspector John Canning said contractors working on clearing the slip yesterday morning suggested that Mr Manera look in a particular area near the slip.
Mr Canning said the "guts" of the campervan had been torn apart in the crash.
"All we initially found was the chassis and wheels; the rest of the rental vehicle, including the engine and gearbox, are gone."
Police had so far been unable to confirm whether the couple were in the vehicle when it left the road, but search and rescue crews were scouring the area from the crash site to the river mouth on foot, by boat and from the air.
"It is going to be a big job; at the time the couple crashed, the Haast River was running very high."
Mr Manera said he did not believe the pair had ignored any weather warning signs not to travel in the area, or road closed signs.
The New Zealand Transport Agency confirmed today that the pass was closed at 8pm on Tuesday, and Mr Manera said the couple would have driven into the area prior to the road closed signs going up because of the treacherous and windy conditions. The slip occurred later.
"They would have been there lawfully and not breached any road blocks or warnings."
Mr Hayes' older brother Liam spoke to the New Zealand Herald last night saying that the family was holding out hope the couple were alive.
He said their spirits were "not the greatest, but still optimistic" and they had no immediate plans to come to New Zealand. "Connor brought Joanna to New Zealand to get her settled for her new job. (They have) both done a lot of travelling before," Mr Hayes said.
He had been receiving regular updates from his brother, who was due to start training for Canada's police force on his return, but that stopped last week.
"They were having a great time. He had been sending email updates to my family; the last one on September 8. He was going on a glacier tour on the 10th and that's his last-known whereabouts."
The couple had been dating for almost two years.
A Twitter feed, #findjoandconnor has been set up for messages of support and hope and to encourage searchers to keep going.