Updated Thursday 11:30 a.m. ET. This is a developing story and will be updated as more information becomes available.

A blizzard and avalanches in Nepal's Himalaya Mountains have killed hikers, guides, and herders in a popular trekking region, government officials said Wednesday. More than two dozen people are feared dead and many others remained missing days after the disaster.

Reports on the casualties varied, with rescue efforts for stranded or injured trekkers hindered by snowfall. The Nepalese Tourism Ministry reported the recovery of 23 dead bodies, including 18 foreigners, by Thursday.

The highest death toll—with more than a dozen deaths—seem to have come on Nepal's Thorung La pass, the highest point at 17,770 feet (5,416 meters) in elevation on the Annapurna hiking circuit, says Jiban Ghimire, a guide and outfitter based in Kathmandu.

At least 250 people had registered to hike through at a police checkpoint before the blizzard hit, Ghimire said by email on Thursday. "There must be lot of people in [a] trap. We have to wait and see today."

View Images Martin gamache and Maggie Smith, NG STAFF SOURCES: Government of Nepal, Ministry of Culture, Tourism & Civil Aviation; BBC; Guardian; New York Times

The Annapurna circuit is popular with casual hikers, who flock to the region for October's typically mild weather.

"More helicopters and rescuers will also be mobilized tomorrow to intensify the search and rescue operations in the affected sites," said a Tourism Ministry statement.

Inexperienced Hikers, Real Mountaineering

The disaster on the Annapurna comes six months after an avalanche that killed 16 mountain workers, including 13 Sherpas, on Mount Everest, the world's tallest mountain at 29,035 feet (8,850 meters). The Everest workers were involved in helping high-paying customers through the rigors of scaling Everest, which typically draws experienced high-altitude climbers. (Read about how April's deadly Everest avalanche unfolded.)

By contrast, the Annapurna circuit, roughly 200 miles (320 kilometers) west of Everest, is a much less demanding hike that attracts a range of tourists from around the world.

"Most trekkers on a route like the Annapurna circuit would have no mountaineering experience whatsoever. They'd be hikers, maybe without much wilderness experience," says Adrian Ballinger, owner and head guide of Alpenglow Expeditions, based in Olympic Valley, California.

During autumn, the 150 mile (241 kilometers) circuit usually sees mild weather and snow is relatively rare, Ballinger said. "But in a storm condition, all of a sudden you're in extremely high altitude," he said. "It turns into real mountaineering."

View Images Tuesday's avalanche happened on Nepal's Thorung Pass. Photograph by Himalayan Heart, EPA

Unexpected Avalanches

An unexpectedly heavy snowstorm fell on the Annapurna range on Tuesday.

"Unexpected snow brings unexpected avalanches," says Karl Birkeland of the U.S. Forest Service National Avalanche Center in Bozeman, Montana. "Any time you have heavy snowfall with wind-borne snow you are increasing the odds of avalanches."

The most deadly avalanche during the storm, Ghimire said, citing accounts from Nepal's Tourism Ministry, killed five Slovakian mountain climbers and three Nepali guides at the base camp beneath Mount Dhaulagiri, the seventh-highest mountain in the world.

Weather forecasts are hard to come by in the region, Ballinger said, which may have left hikers unprepared for the storm.

The blizzard followed heavy rains that battered Nepal and India earlier in the week, triggered by the remnants of Cyclone Hudud, which itself killed at least eight people and displaced 400,000 more from coastal regions.