Six climbers on Mount Rainier likely fell a thousand metres to their deaths in what would be among the worst alpine accidents ever on the iconic Washington state mountain.

A helicopter crew on Saturday spotted camping and climbing gear in the avalanche-prone area.

It’s believed the group fell 1000 metres from their last known whereabouts of 3900 metres on Liberty Ridge, Mount Rainier National Park spokeswoman Patricia Wold said in a statement on Sunday.

“There’s not a viable chance of survival,” park Ranger Fawn Bauer said.

Air and ground searches were suspended late on Saturday afternoon. The danger of falling rock and ice in the area where searchers picked up the pings prevents a ground recovery effort.

“It would expose our rangers to pretty extreme conditions,” Bauer said.

“And, in all honesty, we may never be able to get on the ground there.”

Aircraft will survey the area periodically in the coming weeks and months, Wold said, but the possibility of recovering the six is uncertain.

The missing group includes four clients of Seattle-based Alpine Ascents International and two guides. They were due to return from the mountain on Friday. When they did not return, the climbing company notified park officials.

The loss of life would be among the deadliest climbing accidents ever on the peak in the Cascade mountain range.

In 1981, 11 people were killed during a guided climb when they were struck by a massive ice fall on the Ingraham Glacier.

Mount Rainier, southeast of Seattle, stands at 4392 metres and attracts thousands of climbers trying to reach its summit every year.