Revelers rush up a hill after panic broke out Saturday during the Love Parade festival in Duisburg, western Germany. At least 19 people were killed in the incident. Photo: AFP

Authorities were searching for clues Sunday as to what touched off a sudden stampede at the Love Parade dance party in Duisburg, western Germany that killed at least 19 people.

Around 340 others were injured as a crush occurred in or around a tunnel leading to the day-long open-air festival, attended, officials said, by some 1.4 million revelers.

The exact causes of the disaster were unclear and it was not certain whether foreigners were among the dead at the event, which attracts thousands from all around the world.

Police initially said the crush happened in the tunnel itself but an official from Duisburg, a city of 500,000 people just north of Dusseldorf, said others also died on steps leading toward the tunnel.

No further details were immediately available about the dead, which earlier police reports said included nine women and six men. A doctor from the nearby Johanniter hospital said some 20 to 30 more people were badly injured.

Most revelers remained unaware of the incident and continued dancing and listening to the music long afterward as authorities kept a lid on the news to avoid another panic.

Eyewitnesses said the horrific scenes were “unimaginable.” One witness told the NTV rolling news channel that several people had fallen to the ground and had been trampled underfoot.

Panicked friends and family sent a raft of messages on Twitter in a bid to locate missing partygoers.

Chancellor Angela Merkel said she was “aghast” at the catastrophe. “In these difficult hours, my thoughts are with the relatives of the victims. They have my sympathy and my condolences.”

Rescue work was initially hampered by the huge crowds attending one of Europe’s biggest electronic music events in fine weather, officials said.

Shock turned quickly to anger as partygoers criticized organizers for only allowing one entrance through the tunnel to the festival. There was “simply nowhere to get out” of the area around the tunnel, one survivor told WDR television. The influential mass circulation daily Bild asked on its website: “Why did the police let people carry on the party?”

The Love Parade annual event with a backdrop of electronic dance music was first held in Berlin in 1989 to promote peace through music and gradually grew into a massive outdoor celebration. Organizers could not immediately be reached for comment. Police said an investigation had already begun.

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