The train derailed along the mountains near Tiefencastel, between Chur and St. Moritz in Graubünden.
Authorities have not yet released any information about how many people were injured or if there were any fatalities, but are categorizing the derailment as a "serious" incident.
The injured are being airlifted to local hospitals.
Passenger Steven Bueller described the ordeal to Swiss radio saying, "We all went to the back to shift the weight, to try to stop it from pitching into the ravine. It was a nightmare scene with many terrified people aboard."
Official reports have only confirmed that one car fell into the ravine, but on Twitter, some are saying a second plunged off the cliff since reports broke.
BREAKING: Swiss train derailed by landslide in country's east as several carriages have plunged into ravine. pic.twitter.com/CNra5csuXo— The Int. Spectator (@INTLSpectator) August 13, 2014
The incident comes two days after three people were killed when a Swiss train crashed into their minibus in Wolfenschiessen.