(UPDATE, 10:17 pm) The Missoula County Sheriff's Office says that the two riders who were unaccounted for after the slide have been pronounced dead.
The third rider who was able to call 911 was brought out with search crews and did not need medical assistance.
The Sheriff's Office says that the names of the deceased will not be released until all family members have had the proper notification. They added: "Please keep these families in your thoughts and prayers."
(UPDATE, 5:22 pm) The Missoula County Sheriff's Office posted an update at 5:19 pm: "Search and rescue crews are making their way to the avalanche affected area, but weather conditions are extremely tough. The National Weather Service has predicted that search conditions through this evening into tonight will include wet snow and windy conditions. Wind speeds are expected to reach up to 60 miles per hour. The wet nature of the snow will result in compacting accumulation, but an additional 6 to 10 inches of snow are expected tonight with 1 to 3 inches on Thursday. Temperatures will slowly cool tonight, with wind chill readings possibly approaching zero by the early morning hours Thursday. Please keep these folks in your thoughts as they head up into tough conditions."
Search and rescue teams are responding to reports of an avalanche in the Seeley Lake Area.
The Missoula County Sheriff’s Office reports that at approximately 2:15 p.m. on Wednesday 9-1-1 dispatchers received a call from a person who said he had been snowmobiling in the Dinah Lake area when he got caught in an avalanche. The caller indicated he was able to get out but that two others were buried in the slide.
Seeley-Swan Search and Rescue, Missoula County Search and Rescue, Missoula Emergency Services and the Seeley Fire Department are organizing a search for the lost individuals.
The avalanche danger is considered high in several areas of Missoula County according to the National Weather Service. Very dangerous avalanche conditions exist and travel in avalanche terrain is not recommended.