( CNN ) -- A 25-year-old woman who was injured in last week 's stampede at the Love Parade music festival in Duisburg , Germany , died Wednesday , bringing the death toll to 21 , prosecutors there said . The deadly crush happened Saturday in an underpass between the main event site and an expansion area . Witnesses told CNN affiliate NTV that people pushed into the tunnel from both sides until it was dangerously overcrowded . The panic began when people began to lose consciousness as they were crushed against the walls and each other . The Duisburg public prosecutor 's office said 511 were injured . Of these , 283 people had to be treated in hospitals , and all but 43 have been released . German Chancellor Angela Merkel has called for a thorough investigation into the incident and said that she was `` horrified and saddened '' by the tragedy . Carsten Lueb of NTV said some 1.4 million people showed up at the popular Love Parade festival , which featured dozens of DJs spinning techno music for hours . Organizers expected only 700,000 to 800,000 attendees , so to accommodate more people they opened an additional event site . The numbers are disputed by police , who say the area can hold between 250,000 and 350,000 and at no time was it filled to capacity . NTV reported that 1,400 police officers were on hand to monitor the event . Detlef von Schmeling of the Duisburg police said more than 4,000 police officers provided security . Witnesses told NTV that police were warned at least an hour before the incident that the underpass was becoming dangerously crowded . An additional entryway had been opened before the accident to relieve some of the pressure . Police are investigating how the back-up came to occur in the underpass .
Twenty-one people have died in the tragedy . More than 40 remain in hospitals . The German chancellor wants a thorough investigation .