The incident took place at a concert of rapper Casper and hip hop artist Marteria at about 9 p.m. local time (19:00 GMT) on Saturday, Die Welt newspaper reported.
According to the local fire department, the LED screen collapse might have been caused by stormy weather.
The victims were hospitalized, with some 150 people examined by medics at the scene. Two were seriously injured, while 18 others sustained minor injuries.
According to various estimates, between 18,000 and 20,000 people attended the concert. As a result of the incident, the concert was stopped.