A fire-safety expert from German inspection agency TueV said on Friday (January 2) it seemed unlikely that the bar's roof met fire retardant standards and could have contributed to the rapid spread of the fire that engulfed a crowded bar and killed around 40 people at a New Year's Eve party in the Swiss ski resort of Crans-Montana.

"If I have a material that is flame retardant, it stops burning when the ignition source is removed. And here, we have seen in the reports that the fire continued to spread even after the ignition source was removed, and that it spread very quickly. Therefore, I do not assume that the material on the ceiling was flame retardant," Ralf Hoehmann said from TueV's Frankfurt offices.

Hoehmann said the conditions for a flashfire had likely been met giving people only very little time to react to the situation.

"Flashover is a phenomenon of fire, so it is not a cause of fire, but rather a development of fire, where in the initial phase there is heavy smoke development, which then combined with intense heat development can lead to flashover. This typically takes place over a period of approximately 120 seconds," Hoehmann said, adding that the fact that the fire started in the lower ground floor and may not have had enough exit routes would have led to panic.

"Of course, it's impossible to assess from here, but in Germany, one would say that the lack of a second escape route, structurally speaking, would result in a prohibition of use. Because if the first escape route doesn't work, then everyone is trapped there like in a mousetrap and have no chance of leaving the building, especially if it's in the basement. It's not critical on the ground floor, nor on the upper floor if there is a second external staircase, but it's difficult in the basement. The question that arises is whether the building was approved as a meeting place for up to 200 people," Hoehmann told Reuters TV.

Police said the fire broke out at 1:30 a.m. (0030 GMT) as revellers were celebrating in a bar called Le Constellation in the resort in southwestern Switzerland, which locals said was popular with teenagers.

The cause of the blaze, which was initially reported as an explosion, remained unclear but authorities said the fire appeared to be an accident rather than an attack.

Authorities warned that naming the victims or establishing a definitive death toll would take time because many of the bodies were badly burned. Experts were using dental and DNA records to try to identify the dead.

Production: Timm Reichert, Tanya Wood/Reuters