In this story:

• Scattered shoes
• 'Not a normal fire'
• Race to escape
• Related stories and sites

More than 60 injured were reportedly in critical condition, many suffering from severe burns.

Parents and young people gathered outside the Macedonian Association building, where the fire broke out shortly before midnight, to lay flowers and light candles in memory of their loved ones.

As may as 400 people, most ages 13 to 18, had crammed into the building for the dance. The association's permit reportedly only allowed up to 150 people.

Officials said Friday the building did not have sprinklers, and was not required to have them.

There were only two exits in the building, one of which was blocked by flames, officials said.

Investigators were still on the scene Friday afternoon, combing the gutted structure for clues to the fire's cause.

Scattered shoes

The crowd gathering outside the structure had swollen to several hundred by midday.

Swedish Prime Minister Goran Persson fought back tears when he visited the scene.

Persson said the horror of the tragedy began to sink in when he saw children's boots scattered around in the ruined disco.

"It was all burned out, with only a skeleton left," Persson told reporters. "On the floor there were shoes and boots -- boots just like our own children have. It was only then that you could really understand what happened."

Officials said many of the victims were from immigrant families from Macedonia, Bosnia, Yugoslavia and Iran.

'Not a normal fire'

At a news conference early Friday, officials said most of the victims had choked to death on smoke and poisonous gases.

Binan Atta was walking to the association building when he saw the fire. Atta said he raced in and pulled several people to safety -- including a friend.

"Lots of kids were just screaming," Atta said. "I saw about 10 people in windows who just jumped. They didn't even look down" before jumping.

The cause of the fire was not immediately known. But local rescue service leader Lennart Olin said there were signs that the fire was set, TT reported.

"The fact that it spread so fast indicates that it was not a normal fire," he said. Olin said he believed this was the worst fire disaster ever in Sweden.

Investigators were also reportedly checking the possibility that electrical problems may have sparked the blaze.

"It reminded me of the gas chambers at Auschwitz," Olin said, describing the sight that rescuers first saw when they entered the building.

The building had been inspected by the rescue service in April and "fulfilled all possible demands as far as emergency exits and the possibility for fast evacuation," Olin said.

Jamal Fawz, 15, said he was on the dance floor when the blaze started.

"It looked like it started in the ceiling, and lamps and loudspeakers fell to the floor," he said.

"It was chaos. Everybody was trying to get out and people trampled on each other on the way to the exit. ... Others kicked out the windows and jumped out," said Fawz, who estimated there were about 400 people inside.

Ambulances were called in from several nearby communities and the Gothenburg rescue services also brought city buses into service to help transport the injured.

Gothenburg is Sweden's second-largest city, on the country's west coast about 300 miles southwest of Stockholm.

The Associated Press and Reuters contributed to this report.