Obwald cantonal police said the snow slide was reported to them shortly after 11am in the Laub area of the resort.
A 45-year-old Swedish citizen was flown in a helicopter by Rega emergency services to hospital for treatment of “moderate” injuries, police said.
Another Swede, 36, was treated for minor injuries while nine others were uninjured.
Ten of the eleven were able to dig themselves out of the snow unaided, while the other person needed help from fellow skiers, police said.
Seven of the skiers were part of a guided group.
The avalanche was described as being 300 metres wide and 800 metres long, occurring partway down the mountain on a slope identified as “off-piste” on the ski resort’s map.
It occurred at a time when the WSL Institute for Snow and Avalanche Research had issued a warning for the region urging “caution and restraint.”
While it appeared that all skiers survived the avalanche, police and rescue officials took no chances.
Two dog teams joined members of the Engleberg mountain rescue service, the Central Switzerland Alpine rescue service and cantonal police in a search for possible missing people.
Meanwhile, another avalanche injured a British skier on Sunday in the Col des Mines area of Verbier ski resort in the canton of Valais.
The incident occurred at around 10am in an off-piste area at an altitude of 2,600 metres, cantonal police said.
The victim, a 24-year-old man, suffered mild hypothermia after being swept down the slope along with another British man, aged 22, who escaped injury.
They were skiing with a woman who was uninjured.
The avalanche was 600 metres long and 200 metres wide, police said.
The incidents follow heavy snowfalls in the Alps in recent days with many ski resorts opening for the season over the weekend.