KATOWICE, Poland (AP) - Rescuers yesterday abandoned hope 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, visiting 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. Yesterday, 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," Mejer said.

Sixty-six 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 more 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, "The reasons are not clear."

One survivor, Tadeusz Dlugosz, was still at the site yesterday 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.

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 by using their sharp sense of direction.

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