Two men, aged 19 and 24, fell out of the open trunk of a moving car and were injured in the process.
The 19-year-old had to be hospitalized with a head wound, abrasions and bruises, a police spokesman said on Monday.
According to the police's previous knowledge, the car was so full on Sunday morning that the two men who were hitchhiking could only find space in the open trunk.
The driver then accelerated sharply on a district road near Obergünzburg (Bavaria), so that the two young men fell out and hit the asphalt with full force.
The driver drove on, it was said.
The accident victims could not provide information about the driver or the other occupants of the car, as the police spokesman said.
The investigators are now looking for witnesses.