LISA DESJARDINS: Welcome to the "News Hour."

Some 40 people are dead and more than 100 injured, many seriously, after a fire tore through a bar in the Swiss mountain town of Crans-Montana on New Year's just hours after midnight.

Authorities have ruled out a terror attack, but the cause of the fire is still under investigation as the Swiss face a devastating scene.

This was the scene outside Le Constellation, where Swiss authorities say a massive blaze broke out in a packed and popular ski resort bar just after 1:30 a.m.

on New Year's Day.

SAMUEL RAPP, Witness (through translator): There were people screaming and then people lying on the ground probably dead.

LISA DESJARDINS: Many had gathered there to ring in the new year, when the celebration turned suddenly to chaos.

NATHAN HUGON, Witness (through translator): I'm still in shock.

I can't comprehend what happened.

I saw people being resuscitated.

I saw people completely burned.

I saw people dying.

LISA DESJARDINS: Today, as investigators combed through the rubble.

Officials said it will take days to identify all of the victims and that it is still too early to determine the cause of the fire.

But officials say flames likely triggered a sudden back draft explosion.

Eyewitnesses described a rush of people trying to escape a basement bar through a narrow bottleneck at the top of the staircase.

LAETITIA PLACE, Fire Survivor (through translator): The first stairs are pretty easy to get through since they're wide and all that.

But after that, there's a small door where everyone was pushing.

And so we all fell.

We were piled on top of each other.

Some people were burning and some were dead next to us.

LISA DESJARDINS: In the early morning hours, casualties quickly filled local hospitals and some of the injured had to be flown by helicopter or jet to other cities, where doctors raced to stabilize the burn victims.

Those who were there described a desperate scene.

NATHAN HUGON (through translator): I saw people pushing each other, falling down the stairs in a frenzy to escape.

Some were being trampled.

And I know that some couldn't get out and unfortunately died inside.

LISA DESJARDINS: Only adding to the sense of tragedy, most of the victims were young people.

Swiss President Guy Parmelin called it one of the worst disasters in his country's history.

GUY PARMELIN, President of Switzerland (through translator): The events that took place in this public establishment last night constitute a disaster of unprecedented and horrifying scale.

Behind these numbers are faces, names, families, destinies brutally cut short or forever shattered.

LISA DESJARDINS: This morning, as a procession of vans made their way toward the scene of the blaze to transport bodies, the small town was still in shock.

Residents and first responders alike are struggling with hard questions and simple disbelief.