ASHFORD, Washington (CNN) -- All 12 mountain climbers caught in an avalanche of snow on Washington's Mount Rainier Thursday have been accounted for, with rescue workers racing against the approach of nightfall to extract them from the mountain's snowy slopes.

None of the climbers appeared seriously injured. Reported injuries ranged from broken bones to hypothermia. The climbers were to be taken to hospitals in Puyallup and Tacoma.

About 2:30 p.m. (5:30 p.m. EDT), the avalanche hit two six-member climbing parties who were ascending along a route called Disappointment Cleaver at an altitude of about 12,000 feet (3,640 meters).

One group of six people was pushed into a crevasse. Six other climbers, connected by rope, were able to stop their slide by digging their axes into the ice.

Four of the six climbers who were swept into the crevasse were pulled out, but a man and a woman were still inside and suffering from hypothermia, according to Mount Rainier National Park official Nancy Woodward.

Another climber with a cell phone reported the incident to authorities, who dispatched helicopters and rescue teams to the site. Bad weather initially showed the rescue operation.

Warm spring weather likely caused the avalanche, authorities said. Temperatures have recently gone as high as the upper 70s and lower 80s.

An estimated 300 people have died over the last 100 years in avalanches on Mount Rainier, located about 50 miles southwest of Seattle. The worst avalanche in recent history happened on June 21, 1981, when 11 climbers died.

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