She said there was little chance for survival.
The group, from Seattle’s Alpine Ascents International, was last heard from on Wednesday.
There were two guides and four clients in the party, which began a five-day expedition last Monday.
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“We don’t believe there was a viable chance for survival,” she said.
The search effort has been suspended.
The last contact was via satellite phone on Wednesday at an elevation of 12,800ft.
At that time a rain system was sweeping through.
When the party failed to return on Friday a helicopter was despatched.
Mount Rainier stands at 14,410ft and attracts thousands of climbers each year.