The fully-loaded bus was carrying a group of 16 to 21 year-olds from Düsseldorf and nearby towns when it caught fire near the Austrian town of Bischofshofen, about 50 kilometres outside of Salzburg.
The fire started after the bus came across a rear-end collision involving other vehicles on the highway. The bus avoided the collision, but somehow burst into flames shortly afterward, according to police.
The skiers were able to exit the bus safely, but four passengers were treated for smoke inhalation at a nearby hospital. Three people were also injured, two seriously, in the rear-end collision.
Millions of Germans travel to Austria every year to ski. This winter has seen record snowfalls throughout the Alps, with a correspondingly high level of avalanche danger.