Rhineland-Palatinate government spokesman Joachim Winkler told the dpa news agency that there were tips of a possible terrorist attack and that the Rock am Ring festival was shut down on its opening night as a precaution.
"After intensive searches and sweeps of the complete festival site by the police, the suspicion of a potential terrorist threat has not been confirmed", a statement said. "All visitors will be kept informed about any developments on all Rock am Ring social media channels, radio and the speakers".
"In our view, that made the abstract threat far more concrete", said Koblenz police chief Wolfgang Fromm. The backstage passes didn't match those people's real names, he added.
Three people were arrested on Friday night and their homes searched. Set up for day 2 of Rock am Ring has commenced and the program is going to be resumed in the early afternoon.
Some 90,000 people are expected to attend the event which ends on Sunday. The incredibly disciplined fans deserve all our respect and gratitude.
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Security at the festival had been increased following the bombing that killed 22 people at England's Manchester Arena during an Ariana Grande concert in May.
Organizer Marek Lieberberg said 86,000 people left the site within 15 minutes without incident.
Security for the festival had already been increased substantially to 1,200 staff, in response to the May 22 deadly bombing in Manchester, England which occurred after a concert by U.S. singer Ariana Grande.
Overall, some 85 bands were scheduled to play on four stages with Germany's Toten Hosen highlighting Saturday's list and California's System of a Down playing Sunday.
The festival was cancelled past year after scores of ticket holders were injured by lightning strikes.