The accident occurred on a single-track route between Rosenheim and Holzkirchen at 06:48 local time (05:48 GMT)
Officials say they assume both train drivers had no visual contact before the crash as the site is on a bend - and therefore crashed into each other largely without braking
The stretch of line had an automatic braking system designed to halt any train that passed a stop signal. It is not yet known why this failed to stop the crash
Two of the three data recorders or "black boxes" on board the trains have been recovered