The last person rescued alive was pulled out of the debris less than five hours after the collapse.
KATOWICE, Poland -- Rescuers abandoned hope Sunday of finding survivors beneath the wreckage of an exhibition hall that collapsed, killing 66 people, and authorities were bringing in heavy equipment to demolish what little remained of the building.
The structure collapsed Saturday afternoon with an estimated 500 people inside, attending a pigeon racing exhibition. The last person rescued alive from the building was pulled out less than five hours later.
Rescue crews nonetheless worked through the night, using hand tools to carve through the sheet metal and snarled poles of the collapsed building so as not to risk harming any possible survivors as temperatures dropped to 1 degree. On Sunday, a day after the collapse, they stopped.
"The rescue operation is over," said Krzysztof Mejer, a spokesman for the government of the Silesia region. Thirteen rescue dogs from Poland and the neighboring Czech Republic indicated that there were no more bodies in the debris, he said. "We don't expect anyone else to be found under the wreckage."
A total of 66 people were killed and 160 injured, authorities said.
Fire chief Kazimierz Krzowski said heavy machinery would be used to tear down the rest of the structure, which was built in 2000. "The parts of the structure that are not lying on the ground are a threat," he said.
Transport Minister Jerzy Polacek told TVN24 television that the roof was covered with than 18 inches of icy snow, which police blamed for the collapse.
However, the president of the Katowice company that organized the fair, Bruce Robinson, said that "the reasons are not clear."
One survivor, Tadeusz Dlugosz, was still at the site Sunday morning, seeking information on where the body of his 26-year-old son had been taken.
"It was his idea to come to the fair ... and he found his grave there," Dlugosz said. "During the fair he was wearing only a sweater. That could be the cause of his death."
The "Pigeon 2006" fair had more than 120 exhibitors, including groups from Belgium, the Netherlands, Germany, Ukraine and Poland, according to the fair's Web site. The gathering was devoted to pigeon racing, a sport popular in Europe in which homing pigeons are released and race home using their sharp sense of direction.
Frank Schultes said his team of 22 rescue experts, along with six dogs and specialized equipment, were told after traveling from western Germany to offer their help that they were not needed.
"The pigeons are still flying out of the rubble, which means that people could still be living in there," said Schultes, who said his team helped following last year's earthquake in Pakistan.
Grzegorz Rudek, a police spokesman, said the fire chief decided the German team was not needed because Polish dogs were already working at the scene.
Crumpled bird cages were scattered inside the building near the entrance, and white and brown pigeons perched on the twisted rafters.
People who escaped have said two emergency exits were open, but other exits were locked, and that they saw people struggling to break windows to escape.
"I saw a macabre scene as people tried to break windows in order to get out," Franciszek Kowal, who jumped to safety from an outside terrace, told AP.
"People were hitting the panes with chairs, but the windows were unbreakable. One of the panes finally broke, and they started to get out by the window," he said.
Grzegorz Slyszyk, a lawyer who represents the building owner, said he had no information on the reports, but he promised to investigate if exits were locked.
President Lech Kaczynski declared a national period of mourning that will continue until Wednesday and described it as "the greatest tragedy" to hit post-communist Poland.
The leaders of France and Germany, where 15 people were killed when a skating rink collapsed in a similar accident Jan. 2, were among those who offered their condolences. Pope Benedict XVI prayed for the victims; speaking in Polish at the Vatican, he offered his "warm blessing" to the injured and the victims' families.
Thousands of people, among them Prime Minister Kazimierz Marcinkiewicz, packed Katowice's Cathedral of Christ the King for a Mass honoring the victims.
Associated Press Writers Monika Scislowska in Bialka Tatrzanska, Karel Janicek in Warsaw, and Krzysztof Kopacz in Katowice contributed to this report.