At least two people were injured and an unknown number may remain buried in the snow after an avalanche tumbled down a ski slope in the Swiss Alps on Thursday, authorities said.
The avalanche is reported to have hit at around 10:50 a.m. local time (4:50 a.m. ET), at the SkiArena resort in Andermatt, Switzerland, police said in a press release. No fatalities have been reported.
A total of six people had been rescued or freed themselves from the torrent by 4:15 p.m. local time, including the two who were injured. Both were flown to the Uri Cantonal Hospital for treatment by the Swiss Air Ambulance.
Emergency responders with the Alpine Rescue Switzerland, Swiss Air Ambulance and the state police are involved in ongoing rescue operations for anyone that may still remain in the snow, CNN and NBC reported.
“We believe there are more people buried but we can’t say how many,” Reto Pfister, the state police spokesperson for the Swiss canton of Uri, told NBC.
The Swiss Police for the canton of Uri did not immediately respond to PEOPLE’s request for comment.
A video shared with Swiss news outlet Blick shows the snowy mass descend the side of the mountain and directly hit a path of skiers, who can be seen subsequently buried by the snow.
“The longer the search takes, the smaller the chance they get away without an injury or danger to life,” Mathias Gehrig, a spokesperson for Swiss Air Ambulance, told NBC of any remaining skiers who have not been found yet.
Police described the avalanche as a level 3 out of 5, which is marked as a “considerable” danger on the Avalanche Danger Scale.
According to Blick, police are also investigating whether the avalanche occurred spontaneously, or if it was set off by another skier or snowboarder.
Located around 70 miles south of Zurich, the Andermatt ski resort is popular among skiers around the world, CNN reported.