Citing police, Sky News reported that at least 10 people had died in the incident, with some local media saying the figure may be higher. A police spokesperson declined to confirm the number, but said many people were being treated for burns.
The fire broke out at 1.30 am (6.30 am PST) in a bar called “Le Constellation”.
The area has been completely closed off, and a no-fly zone has been imposed over Crans-Montana, police said in a statement, adding that the cause of the blast remained unclear.
More than 100 people were in the bar at the time of the explosion, a police spokesperson said.
This is an emerging story and will be updated with further details throughout the day.