“The lodging had not undergone the safety inspection which is obligatory” and “did not have the characteristics needed to host the public”, said Nathalie Kielwasser, the deputy prosecutor for the city of Colmar.

The guests on the lower floor of the timbered residence all managed to escape alive and it was those on the upper floor who found themselves trapped.

The property was hosting a group of adults with learning disabilities and their companions at the peak of the French summer holiday season in the picturesque area.

The fire brigade said they arrived 15 minutes after the alarm was sounded and could not save more lives as victims rapidly succumbed to the toxic smoke, which often poses more danger in such situations than the actual flames.

“If you want to drive a car, you need a license. If you want to host people, you have to pass this inspection which then tells you how many people you can host and so forth. We impose a certain number of rules for the sake of safety,” Kielwasser said.

The building, an old structure recently renovated, had smoke detectors “but not sufficient for this type of property,” she said.

“The smoke detectors were up to standard but they are not the type of smoke detectors that are placed in properties hosting the public,” she added.

She said it was not yet clear whether there were fire extinguishers in the building. It also what remains unclear what triggered the fire to break out.

The owner of the property, who lives opposite and alerted the firefighters on Wednesday when the fire broke out, is in shock and has not been detained, she said.

Prime Minister Elisabeth Borne, who went to the scene on Wednesday, vowed the investigation would shed “all light” on what she described as an “appalling” disaster.

The traditional semi-timbered building, built in the style of the Alsace region, was heavily damaged by the fire.

Late on Wednesday, a ceremony was held in a local church, with 11 red candles alight in front of the altar.

Local resident Solange Halter, 61, said,“We were woken up by our son very early. When we went outside, we saw a huge plume of smoke”.