The blaze, which ripped through a building where ski season workers were staying in the early hours of Sunday, has shocked one of the most upmarket resorts in the French Alps. It left 25 people injured, four of them seriously.
“We are treating seriously the theory that this could have been a criminal act, but we do not have enough evidence to be able to identify the perpetrators,” local prosecutor Anne Gaches told reporters.
Investigators believe a flammable chemical may have been used to help the fire spread, Gaches added.
“The victims smelt petrol just before the fire, and witnesses also said they had smelt petrol a month earlier,” she added.
The former hotel houses around 60 people working for a hotel company in Courchevel, which is home to many luxury resorts and numerous Michelin-starred restaurants.
A 32-year-old woman and a 50-year-old man, both of whom had been working in mountainside restaurants, were killed in the fire.
Investigators have determined that the blaze broke out on the second floor of the 1970s building, which was due to be refurbished, before spreading to the third floor where the bodies were found.