Eight people were killed when two trains collided head-on in southeast Germany on Tuesday, police said, adding about 150 people were injured, including 50 seriously.

The collision took place on a single track, and one train was derailed, said a police spokesman.

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The cause was unclear and police said that, alongside the rescue effort, investigations were starting to establish what had happened.

The crash between two local passenger trains happened at 6:48 a.m. local time near Bad Aibling in the southern state of Bavaria near the border with Austria.

Dozens of rescue teams were on site, and helicopters carried some of the injured people to nearby hospitals. The area was sealed off.

The trains' operator, Meridian, is part of French passenger transport firm Transdev, which is jointly owned by state-owned bank CDC and water and waste firm Veolia.

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It runs train, tram and bus networks in 19 countries and had revenues of 6.6 billion euros in 2014.

State-owned Deutsche Bahn is responsible for the track. The line has a system that makes a train brake automatically if it goes through a red light.