DUISBERG, Germany, July 24 (UPI) -- A panic-sparked crowd stampede at a German music festival Saturday killed 18 people and injured dozens more, authorities said. Panic broke out and victims were crushed after hundreds of thousands of people attending the Love Parade electronic music festival in Duisburg tried to gain access to the festival grounds through a tunnel too narrow for the mass of people, The Guardian reported Saturday. The New York Times, which reported the death toll had reached 18, said it had yet to be determined what triggered the deadly incident but police said they had told the crowd to reverse directions because of overcrowding shortly before it happened. The Daily Telegraph, which reported 40 people were injured in addition to those killed, said officials estimated between 500,000 and a million people converged on the city for the day-long techno music event. "It was hell," Karl Lowenstein, 21, of Bielefeld told the Telegraph. "The tunnel was dark, it was full. Something happened -- whether someone tripped or someone fell I don't know. But there was a stampede to get to the other end and those who fell … well, many of them never got up again." Emergency medical personnel had difficulty reaching the crushed victims, the BBC reported. There were signs earlier in the day that Duisburg was finding it hard to cope with the sheer numbers of fans trying to get to the event at an unused freight train depot on the outskirts of the city, The Guardian said. City officials reportedly chose not to evacuate the festival grounds immediately, fearing it might spark more panic. One police official described the scene as "utter chaos." "We have to get to the bottom of what actually happened here." Duisburg Police Chief Jurgen Kieskemper said.