Two well-known Utah climbers are missing in Pakistan, where they were attempting to make a treacherous ascent up an icy mountain.

Alpinists Kyle Dempster and Scott Adamson were due back at base camp on Aug. 26. They left five days earlier to begin an ascent up the north face of a place called “Ogre II” off the Choktoi Glacier in northern Pakistan, said Jonathan Thesenga of Black Diamond Equipment. The Utah-based outdoor company sponsors Dempster.

Snowy and cloudy conditions are hindering rescue efforts that began Sunday, he said. Four guides — known as porters — have climbed up the mountain and are hoping to look for Dempster and Adamson with binoculars. They also have extra food, sleeping bags and tents if they find them.

The Pakistani government has offered to send military helicopters if weather permits, Thesenga said.

Dempster, 33, and Adamson, 34, are two of the most accomplished alpinists of their generation, he said.

They nearly died making the same attempt last year in the same spot, Thesenga said. Dempster broke his leg after a 100-foot fall and both men fell 400 feet while trying to get down the mountain. He said the duo hoped they had learned from their mistakes during the near-death experience to make it this time.

Six other climbers, including two from the United States, who were on the mountain are at base camp and ready to ascend if they can help, he said.

The climbers’ girlfriends and family are worried, but everyone is holding out hope that their years of experience on mountains will help them survive.

“They have built their careers on cutting-edge Alpine ascents from Pakistan to Alaska,” Thesenga said. “We remain optimistic that they are going to get out of the mountains and have this amazing story of survival to share.”