The open-air festival, Rock am Ring, was halted on its opening night on Friday after police said there was a concrete terrorist threat. Some 90,000 concertgoers had to return to camping sites outside the venue just before a headliner show from Rammstein.
The Welt newspaper said the suspects worked for a company that helped organize the annual festival. One of them allegedly belongs to the ultra-conservative Muslim Salafi movement.
The three-day concert was scheduled to run through Sunday. Roger Lewentz, interior minister of the German state of Rhineland-Palatinate, said the decision on whether the concert would be allowed to continue would be taken on Saturday. A press conference is slated for 11:00 a.m. local time (9:00GMT).