Eight young men died at the scene and another died of his injuries a few days later as fans crowded in to hear Pearl Jam play June 30 at the Roskilde Festival.

The victims were from Denmark, Sweden, Germany, the Netherlands and Australia.

After a three-week investigation, police decided the festival’s organizers were not responsible for their deaths, Police Chief Constable Uffe Kornerup said

Slippery mud due to heavy rains worsened the situation at the outdoor festival in Roskilde, 25 miles west of Copenhagen, he said. About 74,000 tickets had been sold for the day’s performances.

Security measures included physical barriers designed to prevent overcrowding.

“It’s normal that young people push and squeeze at rock concerts, but here it sadly developed in a catastrophic way,” Kornerup said .

It was the first major accident at the four-day festival, which was first held in 1971 and was inspired by the 1969 Woodstock Festival in upstate New York .