The grounds at the annual Roskilde Festival were muddy from an all-day rain Friday. The victims, all men, slipped or fell in front of the stage and were trampled to death, police said.

The crush occurred shortly before midnight, as Pearl Jam was playing on the main stage before a crowd of about 50,000 people.

“Things were really great and we wanted to move up,” festival-goer Lasse Aagaard told the TV2 channel Saturday morning.

“The pressure from behind was too great,” added Holger Hougaard, another fan who was up front.

The band asked the crowd to move back, and halted the performance when that didn’t happen.

“This is so painful. I think we are all waiting for someone to wake us and say it was just a horrible nightmare,” Pearl Jam said in a statement Saturday. “There are absolutely no words to express our anguish in regard to the parents and loved ones of those precious lives that were lost.”

Victims included a 23-year-old Dutch man, a 26-year-old German, a 22-year-old Swede and 17-year-old Dane. Police withheld other identification details pending notification of relatives.

“Everybody at the festival is deeply concerned and wish to express their sympathy to the relatives,” festival spokesman Leif Skov said.

Danish Prime Minister Poul Nyrup Rasmussen said in a televised interview that “it was a terrible and tragic accident. It is very difficult to put words on the fact that so many young people have lost their lives in such sinister circumstances.”

Erik Olsen, 17, of Norway, said people climbed on top of each other to get air. “The guy in front of me was so shocked he simply screamed. It was impossible to get anywhere,” he told the Stockholm-based tabloid Expressen.

After the stampede, the next main-stage show by the British band The Cure was canceled in “respect for the dead,” Skov said. The deaths were announced over loudspeakers and some concert-goers began crying and others lit candles, Danish media reported.

The festival is expected to continue” to its Sunday conclusion, Skov said, “with the deepest respect for the perished. Life is stronger than death.”

The festival featured 170 performers including Lou Reed, Willie Nelson, Iron Maiden and the Pet Shop Boys.

The Roskilde Festival, first held in 1971, was inspired by the 1969 Woodstock Festival in upstate New York. It is held annually on a farm in Roskilde, 25 miles west of the capital, Copenhagen.

Carsten Iversen, who has supervised concert security in recent years, said Roskilde organizers are very conscientious when it comes to safety.

They “always have said that they wanted it to be the safest festival, and that is very visible,” Iversen said.

The event, which in recent years has appeared on MTV, attracts visitors from most of northern Europe.