Rescue workers stand beside a burnt-out coach on the motorway A9 near Muenchberg, southeastern Germany, Monday, July 3, 2017 after a bus crashed into a truck and caught fire. Picture: News5 / Fricke/NEWS5/dpa via AP

Muenchberg - Eighteen people are thought to have died when a tour bus collided with a semi-trailer and burst into flames in the south of Germany, German police said on Monday.

A total of 30 passengers were injured - many seriously - in the accident on the A9 motorway north of the city of Nuremberg.

A total of 48 people, including two drivers, were on the bus, police in the nearby town of Bayreuth said.

Several rescue helicopters joined about 200 emergency workers and fire officers at the scene of the accident, which occurred in heavy traffic at about 0500 GMT.