PESHAWAR, Pakistan (AP) — Two Japanese climbers went missing on Saturday while attempting to scale K2, the world’s second-highest mountain in northern Pakistan, officials said, the fourth such incident in less than two months.

The latest incident happened when the pair fell from a height of 7,500 meters (24,605-foot) while trying to ascent the 8,611-meter (28,250-foot) high K2, which is also referred to as the “killer mountain,” a regional officer, Waliullah Falahi told The Associated Press by phone.

Two Pakistan army helicopters quickly launched a search and rescue operation but they could not pluck the Japanese because the men didn’t make any move, Falahi said.

He added that a ground search would be launched on Sunday for the Japanese.

The secretary of the Alpine Club of Pakistan, Karrar Haidri, said he was aware of the incident in which two Japanese went missing on K2 and “we are hoping for a miracle, and miracles do happen after such incidents.”

Earlier this month, rescuers found the body of Hiroshi Onishi, 64, who fell into a crevasse on the 7,027-meter (23,054-foot) Spantik Peak, also known as Golden Peak. He was the third Japanese to die on the Golden Peak in less than two months.

Every year, hundreds of climbers try to scale mountains in northern Pakistan, including K2 and Nanga Parbat, and each year several die.