The collision, which involved two Meridian passenger trains, occurred in Bavaria, the town of Bad Aibling, about 25 miles southeast of Munich, according to police spokesman Juergen Thal Meier, cited by the rosenheim24 news portal.
While the death toll is still unknown, local media report at least 150 people have been injured in the crash.
"Some have died, but we don't know exactly how many," a police spokesman told the broadcaster.
Police scheduled a press conference on the fatal train crash for 12 pm local time.
#Bahnunglück Bad Aibling: Pressekonferenz um 12:00 Uhr im Rathaus Bad Aibling (Marienplatz 1)— PolizeiOberbayernSüd (@polizeiOBS) February 9, 2016
The accident took place on the railway line between Rosenheim and Holzkirchen. Several carriages of both trains were derailed, killing "many people" and severely injuring at least 10, with several others sustaining minor injuries.
The reason for the incident is yet unknown, police say.
Police say that at least 12 ambulances and 8 rescue helicopters arrived at the scene. Media report that police officers were also injured in the incident.
Rescue work is on at train collision site in Aibling, Germany pic.twitter.com/HV7gHfmbLI— Khalid Khan (@khalidkhan787) February 9, 2016
According to the train operator's website, the railway line between Rosenheim and Holzkirchen is blocked, which can result in "other delays."
A message for Frau Merkel?