BERLIN – A memorial service will be held for the 20 people crushed to death in a mass panic at the Love Parade techno festival, German officials said Tuesday, as hundreds of people lit candles, left notes and placed flowers at the site of the tragedy.

People in the western German city of Duisburg gathered to express their grief near where the victims died and 500 others were injured in a jammed tunnel that was the lone entry to the annual festival meant to celebrate peace and love.

Some cried and clung to loved ones. Many lined up to sign a condolence book placed between two red candles in the middle of the tunnel.

People also expressed deep anger at city authorities, particularly Mayor Adolf Sauerland, whom they blame for failing to adequately plan for the event. Organizers have come under fire for allegedly trying to squeeze as many as 1.4 million revelers into too small a space and for allowing only one access point onto the grounds.

One note read: "Sauerland, resign! You failed."

Chancellor Angela Merkel and President Christian Wulff will attend the ecumenical ceremony at a church in Duisburg on Saturday, according to their offices. Merkel's office said she would interrupt a summer vacation to attend.

The mayor, however, will not attend given the anger toward him, according to a report by the local Rheinische Post newspaper. The newspaper also said he has received death threats.

The cause of death for all 20 victims was chest contusion, meaning they were crushed to death, said Hannelore Kraft, the state governor of North Rhine-Westphalia, where Duisburg is located.

There has been some confusion about what exactly triggered the mass panic, and some have speculated that the chaos began after some of the victims fell to their deaths from a ramp they had climbed to escape the crush of the crowd.

But the results of their autopsies, announced by Kraft, ruled that theory out.

The last person to die was a young German woman who was buried beneath several others. She was unconscious for two days in the hospital before succumbing to internal injuries late Monday, according to Dr. Martin Pfohl, a physician at the Bethesda hospital in Duisburg.

The Love Parade was once a Berlin institution, but was held for the last time in the capital in 2006 after suffering from financial problems and tensions with city officials over cleanup costs.

It started rotating around the cities of the Ruhr industrial region in 2007, though last year's designated host, Bochum — a smaller city than Duisburg — canceled it over concerns that the event lacked the infrastructure to cope.

Organizers said Sunday that the Love Parade will never be held again.