An Estonian mountaineer who fell into a deep crevasse Sunday has been rescued, but her three fellow hikers remain missing, Peruvian officials said Tuesday

The group, which included some of Estonia's most renowned mountaineers, fell into a 65-foot (20-meter) deep crack on Sunday after an avalanche shook the snowy Cordillera Blanca mountain range in the Andes of northern Peru.

Annemai Martson, a gynecologist, was taken to a clinic Tuesday with two fractured ribs and symptoms of dehydration.

Rescuers were unable to make contact with the rest of her party, according to team leader Alfredo Quintana. The other hikers fell before Martson and, unlike her, and were covered by the snow, dramatically reducing their chances for survival, Quintana said.

"With an avalanche, you have about 30 minutes to save a person. After that, the possibilities are very slim," he said.

Quintana called Martson's survival after more than a full day in the crevasse at subfreezing temperatures a miracle. Rescuers made contact with her on Monday morning, and spent 18 hours carrying her down the mountain.

The hikers, aged between 36 and 45, were highly experienced, according to reports in Estonian media.

One of them was Tarmo Riga, often described as Estonia's best mountain climber, with a record of more than 20 years climbing the world's highest peaks, according to broadcaster ERR.

His wife Jane Riga, a guide and interpreter, was also in the group. The fourth was identified as Allan Valge.

Estonia, a European nation of 1.3 million people, has no mountains of its own.

The high climbing season in Peru runs from May to September, with thousands of adventure-seekers flocking to the Cordillera Blanca.

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Associated Press reporter Jari Tanner reported from Helsinki, Finland.