Ambulances were still parked outside the bar hours later, and broken windows could be seen. Local media described a “smell of burning still in the air”.
Swiss daily Blick cited a doctor at the scene suggesting that the death toll could be in the “dozens”.
Regional daily Le Nouvelliste also said its sources were describing “a heavy toll”, with “around 40 dead and 100 injured”.
Swiss media suggested that the fire may have started when pyrotechnics were used during a concert, but police said the cause was unknown.
Police spokesman Gaetan Lathion told AFP earlier there had first been an “explosion of unknown origin” at around 1.30am at Le Constellation.
Police said the area was “completely closed to the public”, and that “a no-fly zone over Crans-Montana has been imposed”.
“The party was in full swing… music and champagne flowing freely,” a resident who said they lived nearby told 24 heures, a Lausanne newspaper.
But as news of the fire broke, they said, the carefree mood vanished, and people began gathering in the street. “We could hear the sirens in the distance. Around me, people were stunned, worried, silent.”
“We heard helicopters all night long,” another neighbour told 24 heures.
“With the fireworks, we didn’t understand what was going on at first. Then we saw the smoke. It’s terrible, a lot of young people go to that bar.”
