ISLAMABAD, FEBRUARY 07

An aerial search was underway Sunday to find three experienced climbers who lost contact with base camp during only the second winter ascent of K2, the world's second highest mountain, officials said.

Karrar Haideri, a top official with the Alpine Club of Pakistan, said army helicopters resumed the search in northern Pakistan that began a day earlier for Pakistani mountaineer Ali Sadpara and his two companions, John Snorri of Iceland and Juan Pablo Mohr of Chile.

The three lost contact with base camp late Friday and were reported missing Saturday after their support team stopped receiving reports from them during their ascent of the 8,611-meter (28,250-foot) high K2 mountain, sometimes referred to as "killer mountain."

K2, located in the Karakorum mountain range, is one of the most dangerous climbs. Last month, team of 10 Nepalese climbers made history by scaling the K2 for the first time in winter.

"The base camp received no signals from Sadpara and his foreign companions after 8,000 meters ... . A search is on and let's pray for their safe return home," Haideri told The Associated Press.

On Saturday, choppers flew to a height of 7,000 meters (23,000 feet) to try to locate the missing mountaineers with no success.

Pakistan's foreign ministry issued a statement saying Iceland's foreign minister, Gudlaugur Thór Thórdarson, spoke to his Pakistani counterpart, Shah Mahmood Qureshi, by telephone. Qureshi assured him that Pakistan woould spare no effort in the search for the missing mountaineers.

Sadpara and his team left the base camp on Feb. 3, a month after their first attempt to scale the mountain failed because of weather conditions.

Although Mount Everest is 237 meters (777 feet) taller than K2, the K2 mountain is much farther north on the border with China and subject to worse weather conditions, according to mountaineering experts. They say a winter climb is particularly dangerous because of the unpredictable and rapid change in weather conditions.

Winter winds on K2 can blow at more than 200 kph (125 mph) and temperatures can drop to minus 60 degrees Celsius (minus 76 Fahrenheit). In one of the deadliest mountaineering accidents ever, 11 climbers died in a single day trying to scale K2 in 2008.

Haideri said Sadpara's son, Sajid, had returned to the base camp safely after his oxygen regulator malfunctioned at 8,000 meters.

Haideri noted Sadpara's experience as a mountaineer who has climbed the world's eight highest mountains, including the highest, Mount Everest in the Himalayas, and was attempting to climb K2 in winter.