AP has now updated its article.
Says 23 were aboard - 21 Nepalis, and 2 foreigners (China, Kuwait).
Poor weather is hampering search.
The police chief at Jomsom, Harihari Yogi, said they had reports from local villagers of hearing a loud explosion near the small village of Rupshe and attempts were being made to reach there.
[The destination] Jomson is popular for both foreign tourists visiting the Mount Annapurna and Mustang region for trekking, and for Hindu pilgrims visiting the Muktinath temple.