Police said Monday that 12 people had died at a ski resort in Gudauri, northern Georgia, as a result of a fatal carbon monoxide leak.

At the well-known ski station, the victims—11 foreigners and one Georgian—were found sleeping in a space above a restaurant.

Initial investigations showed no evidence of violence on the bodies, according to authorities, who have suggested that an unintentional gas leak is the most likely explanation.

The incomplete burning of fuels like natural gas, wood, or charcoal frequently produces carbon monoxide (CO), a very poisonous, colorless, and odorless gas. CO exposure can cause severe poisoning and oxygen deprivation, which can lead to death.

Local law enforcement is looking into the occurrence, and forensic experts are performing in-depth analyses at the site. The nationalities of the foreign victims have not yet been disclosed.