A stampede killed 19 people and injured 342 at the Love Parade techno music festival in the German city of Duisburg.

"The Duisburg prosecutors office is investigating negligent homicide," prosecutor Rolf Haferkamp said.

Six foreigners, from Spain, Bosnia, the Netherlands, Australia, Italy and China, died in the stampede on Saturday when hordes of young people were pushing through a tunnel into the techno festival grounds at a former freight rail yard.

Authorities were not able to explain how the tragedy happened -- near a tunnel that led to a ramp into the festival grounds.

Most of the victims -- all between the ages of 20 and 40 -- were found dead on the ramp and none in the tunnel, authorities said.

"The question 'Why this happened?' must be answered," Duisburg Mayor Adolf Sauerland said at a news conference. "But there should be no rush to judgment."

The tragedy has shocked a country which is normally well organized about crowd events.

"There must be a very intense examination of how this happened," Chancellor Angela Merkel said in a statement issued from the Bavarian city of Bayreuth. "We must do everything to prevent this from happening again," she added.

Love Parade organizer Rainer Schaller said there would be no more Love Parade festivals.

"The Love Parade was always a peaceful and joyous party that will now forever be overshadowed by (these) tragic events," he said.

"Out of respect for the victims, families and friends, we will discontinue the event.

"The Love Parade is no more."

The free festival, one of Europe's biggest electronic music events, drew about 1.4 million people.