Police in New Zealand are searching on foot, by helicopter and by boat for signs of two Canadians whose rental van was found in a gorge in a remote park on the South Island.

Joanna Lam, 24, and Connor Hayes, 25, haven't been seen or heard from since they were spotted in a park on New Zealand's South Island on Sept. 10. (Facebook)

Joanna Lam, 24, and Connor Hayes, 25, were last seen at Fox Glacier on the afternoon of Sept. 10, according to police.

On Tuesday, police in New Zealand said they had found parts of the couple's rental van.

"A portion of their wrecked rental van was located earlier today [Tuesday] in a gorge off the Haast Pass road at Haast Gates on the west coast of the South Island," police said in a news release.

"The rear wheels and chassis of the vehicle were located about 80 metres down a bluff in the Haast River. The body of the vehicle and engine have not yet been located."

Police don't yet know whether Lam and Hayes were inside the vehicle when it left the road.

Bad storm a week ago

New Zealand police spokeswoman Barbara Dunn said the vehicle was likely swept away in fast-moving floodwaters.

Dunn said the area where Lam and Hayes' vehicle was found experienced a bad storm last Tuesday, but declined to speculate on what happened.

"Until we get some evidence we don't know we've got a serious crash investigation underway but at this stage... we are keeping very much an open mind as to what's happened," said Dunn.

Ceinwen Curtis, a reporter with Radio New Zealand in Christchurch covering the search said there have been a number of landslides at that mountain pass near where the couple's vehicle was found.

She said boulders as big as houses remain on the road, a week after the storm.

'She was just so excited and optimistic,' friend says

A friend of Lam, Tamara Sagadore, said Lam and Hayes — who had been living in Ottawa — had been travelling on the South Island.

She said Lam failed to show up at her new job as a medical imaging specialist for a radiology department in New Zealand on Monday.

Sagadore said Lam and Hayes have been dating for almost two years. They met and lived together in Ottawa, and she said they're a perfect fit.

Hayes, whose family is from the Toronto area, was said to be passionate about running. Lam grew up in Kingston, Ont., where her family still lives.

"He's a great guy; I've met him a couple of times," Sagadore said.

"I think it's just really difficult because everything's so unknown, especially because it's from such a distance. I spoke with her right before she left and she was just so excited and optimistic, and now this happening. It's almost unfathomable."

Lam's aunt, Jennifer Lam, told CBC News that her niece's last Facebook post was made on Sept. 8, two days before she was last seen.

"I'm being very optimistic and wishing for the best," she said, through tears. "All my hope is that they're OK."