LONDON — “Several” dozen people were presumed killed and about 100 others were injured early on New Year’s Day in a fire in a resort town in the Swiss Alps, police said.

A blaze of “undetermined origin” broke out at the Le Constellation bar in Crans-Montana at about 1:30 a.m. local time, the Cantonal Police of Valais said in a statement.

Investigators were working on Thursday to determine the cause of the fire, officials said during a morning press conference. The incident was not being investigated as an attack, they added.

“A large contingent of police, firefighters, and rescue personnel immediately responded to the scene to assist the numerous victims,” police said in their earlier statement.

Officials described the emergency response as “major,” adding that the area near the Alpine bar had been closed to the public.

A no-fly zone was put in place over Crans-Montana, police said in their statement.

The resort town is popular with skiers and sits in Switzerland’s southern Sierre District in the Canton of Valais.

Police have not yet identified any of those who were killed in the blaze. Officials on Thursday said it was likely that some of the deceased were tourists who’d traveled to the Alpine town to celebrate New Year’s Eve.