Around 200 police and firemen went to the scene of the accident near Dortmund on Friday night, which closed the A2 motorway in both directions through the night.
Police said three semi trucks and two passenger vehicles were involved in the accident on the Autobahn towards Hanover in the German state of North Rhine-Westfalia. All five vehicles burned, and witnesses reported the sound of explosions as emergency services arrived.
The collision occurred at 6:30 pm due to “events that remain uncertain,” police told news agency DDP.
One police officer and one fire department worker were among the six people injured in the accident.
The regional district attorney's office is investigating the cause of the accident.