Around 40 dead, 115 injured in Swiss Alps resort fire on New Year's Day, police say

LONDON -- Around 40 people were killed and 115 others were injured early on New Year's Day, when a fire ripped through a popular bar in a resort town in the Swiss Alps, police said.

The Swiss president said the fire is "one of the worst tragedies our country has experienced."

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 press conference.

A criminal investigation into the fire has been launched by the Public Prosecutor's Office of the Canton of Valais, but officials said the possibility of a terrorist attack has been ruled out.

"What should have been a moment of joy turned into a tragedy in Crans-Montana last night, a tragedy that affects all of Switzerland and the world," Guy Parmelin, the minister who assumed the rotating Swiss presidency on Thursday, said in German on social media. "The Federal Council has taken note of this tragedy with profound dismay."

Parmelin said flags will be flown at half-mast for the next five days to honor those killed.

Officials described the emergency response as "major."

Stephane Ganzer, head of the Valais Cantonal Department of Security, Institutions and Sport, said 42 ambulances, 13 helicopters and three disaster trucks raced to the scene.

Mathias Reynard, president of the Valais state council, said most of those injured are in a "serious state."

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 released the identities of those who were killed in the blaze. Officials on Thursday said it was likely, given the popularity of the area with travelers, that some of the deceased were tourists who traveled to the Alpine town to ski and to celebrate New Year's Eve.

The French Foreign Affairs Ministry said in a statement that at least two French nationals were among the injured. Both were being treated in local hospitals, the ministry said. French officials were "in constant contact with the Swiss authorities in case other nationals are affected," the ministry added.

ABC News' Tom Soufi-Burridge contributed to this report.