A stampede inside a tunnel crowded with techno music fans crushed 18 people to death and injured 80 at Germany's famed Love Parade festival on Saturday.
Thousands of other revelers keep partying at the event in Duisburg, near Duesseldorf, unaware of the deadly stampede that started when police tried to block thousands more people from entering the already-jammed parade grounds.
Police are still trying to determine exactly what happened, but the situation was "very chaotic," police commissioner Juergen Kieskemper said.
He said police closed off the area where the parade was being held because it was already overcrowded. They told revelers over loudspeakers to turn around and walk back in the other direction before the panic broke out, he said.
German news agency DAPD reported the victims were crushed in the large tunnel leading to the event site and that emergency workers had trouble getting to them.
Duisburg city officials decided at a crisis meeting to let the parade go on to prevent more panic and another stampede, said city spokesman Frank Kopatschek.
"The crisis meeting determined not to stop the event because at the moment there are too many people on the grounds," he said.
The Love Parade was once an institution in Berlin, but has been held in the industrial Ruhr region of western Germany since 2007.
"The young people came to celebrate and instead there are deaths and injured," said Chancellor Angela Merkel. "I am horrified by the suffering and the pain."
Criticism quickly fell on city officials for allowing only one entrance to the grounds of a hugely popular event that drew hundreds of thousands of people to dance and listen to DJs spin. German media said 1.4 million people attended but that figure could not be immediately confirmed.
Eyewitness Udo Sandhoefer told n-tv television that even though no one else was being let in, people still streamed into the tunnel, causing "a real mass panic."
"At some point the column (of people) got stuck, probably because everything was closed up front, and we saw that the first people were already lying on the ground," he said.
"Others climbed up the walls and tried somehow to get into the grounds from the side, and the people in the crowd that moved up simply ran over those who were lying on the ground."
Another witness, a young man who wasn't named, told n-tv the tunnel became so crowded that people began falling. "It got tighter and tighter from minute to minute and at some point everyone just wanted out," he said. "People were just pushed together until they fell over."
The original Berlin Love Parade grew from a 1989 peace demonstration into a huge outdoor celebration of club culture that drew about 1.5 million people at its peak in 1999. But it suffered from financial problems and tensions with city officials in later years, and eventually moved.