( CNN ) -- German authorities have indicted 10 people in connection with a stampede at a music festival that killed 21 people in July 2010 . The deadly crush happened at the Love Parade festival in Duisburg . Six city workers and four who worked for the event organizers were charged with involuntary manslaughter and bodily injury caused by negligence , a senior prosecutor said Wednesday . The deadly crush took place between the main event site and an expansion area in an underpass that became a fateful bottleneck . A stampede . Faulty crowd flow planning led people both entering and exiting the festival to cram into the underpass from both ends , Michael Schwarz said in a prepared statement . In addition , barriers that were installed without approval hemmed the crowd in , further increasing the congestion . Witnesses told CNN affiliate NTV that the underpass became dangerously overcrowded , and some people who were crushed against the walls and each other lost consciousness . That triggered a panic in the crowd , unleashing a stampede . The Duisburg public prosecutor 's office said 652 people were injured . Of them , 283 had to be treated in hospitals . Mass festival . Masses of people attended the annual electronica and techno music festival , but there is much disagreement on the size of the crowd . NTV said about 1.4 million people showed up at the 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 . But the numbers are disputed by police , who said that the area can hold between 250,000 and 350,000 people and that it was not filled to capacity . At the time , NTV said 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 . Immediately after the calamity , the Love Parade 's organizers dissolved the festival , vowing never to put it on again . CNN 's Diana Magnay and Ben Brumfield contributed to this report .
NEW : Prosecutor says faulty planning contributed to deadly bottleneck . NTV : About 1.4 million people attended the 2010 Love Parade festival . The affiliate said attendees were pushing into a tunnel from both directions . Police said no more than 350,000 actually attended .