KATHMANDU, Nepal (AFP) — Renowned United States ski mountaineer Hilaree Nelson has gone missing on Nepal's Manaslu mountain, on the same day that an avalanche killed a Nepali climber on the same peak, expedition organizers and officials said Tuesday.

Nelson was skiing down Manaslu after having successfully summited the world's eighth-highest mountain with her partner Jim Morrison on Monday.

"She had an accident yesterday as she was descending shortly after her summit. We are trying to get clarity on what happened," Jiban Ghimire of Shangri-La Nepal Treks, which organized the expedition, told AFP.

On the same day, an avalanche hit between Camps 3 and 4 on the 8,163-meter mountain, killing a Nepali climber and injuring a dozen others, the government's tourism department said.

The death was the first confirmed casualty of the autumn climbing season in Nepal.

Ghimire said that the weather had improved on Tuesday and a helicopter was headed to the site of Nelson's accident.

Morrison safely reached base camp and was accompanying the search and rescue team, Ghimire added.

The North Face, which sponsors Nelson, confirmed the climber was missing.

"We are in touch with Hilaree's family and supporting search and rescue efforts in every way we can," the company said in an Instagram post on Tuesday.

"I haven't felt as sure-footed on Manaslu as I have on past adventure into the thin atmosphere of the high Himalaya," Nelson said in an Instagram post on Thursday.

The 49-year-old has had a career spanning two decades and is described as "the most prolific ski mountaineer of her generation" in a profile on The North Face's website.

In 2012, she became the first woman to summit the highest mountain in the world, Everest, and its adjacent Lhotse within 24 hours.