As an investigation attempts to shed light on what caused a deadly stampede at the Love Parade dance music festival in Duisburg on Saturday, city officials have faced tough questions over the tragedy.

Duisburg Deputy Police Chief Detlef von Schmeling told reporters on Sunday that two criminal reports were pending on the incident, but he could not confirm whether the organizers or emergency services would be implicated in the investigation.

Calls for an "intensive" and "uncompromising" investigation into the causes of the tragedy have come from as high up as Germany's Chancellor Angela Merkel and President Christian Wulff.

Victims from at least seven countries

In total, 19 people were killed when panic broke out in an over-crowded tunnel entrance to the festival. The circumstances that led to the people's deaths remained unclear.People tried to escape the area around the tunnel and may have been trampled to death or fallen from a bridge they scaled to flee the crowd.

Parademics had difficulty getting to the accident site

Von Schmeling said 16 victims who died at the scene were found on a nearby access ramp, indicating they were not killed in the tunnel. He added that prior to the stampede police had opened a second access ramp to ease crowd pressure around the tunnel. He also said that police were responsible for regulating the number of people inside the tunnel.

Sixteen victims have so far been identified, including two Spaniards, a Bosnian, a Dutchman, an Australian, an Italian and one person from China. Von Schmeling said all those who died were between 20 and