Public TV station SRF quotes Vaud canton (state) police spokesman Pierre-Olivier Gaudard as saying one person has yet to be recovered from the wreckage.
The crash happened late Monday on a regional line about 50 kilometers (31 miles) southwest of the capital, Bern.
Pictures on the website of local daily 24 Heures showed the two regional trains locked together but still on the tracks.
Earlier this month, 79 people were killed in a high-speed derailment in Spain.
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