KATOWICE, Poland (CNN) -- Rescuers say that after searching for more than 20 hours in the bitter cold, they do not expect to find any more bodies under the twisted wreckage of an exhibition hall in southern Poland that collapsed during a racing pigeon show, killing 66 and injuring 160.
"There is a low possibility that people are still trapped under there," fire chief Kazimierz Krzowski said Sunday after surveying the rubble of the International Exhibition Hall, on the border of the city of Katowice and the suburb of Chorzow, 350 kilometers (210 miles) southwest of Warsaw.
About 1,300 rescuers, including coal miners, had used hand tools to carve through the tangled sheet metal and poles of the collapsed building in a bid to avoid harming any potential survivors. But Krzowski said heavy machinery was now being called in to tear down the rest of the building.
"The parts of the structure that are not lying on the ground are a threat," he told The Associated Press.
The collapse came during the annual three-day National Exhibition of Racing Pigeons. The event was attended by thousands of people, including families, breeders and exhibitors from Poland and other nations.
About 500 people were believed to be inside when the collapse occurred about 5 p.m. Saturday. About 140 were injured, officials said, of whom 128 were taken to 15 local hospitals.
Family members and bandaged survivors gathered at a crisis center waiting for information on loved ones.
"There are people in there covered in blood, pinned down," said a woman whose father was missing. "There are people moaning and screaming."
A spokesman for the provincial governor said 66 people had died while fire brigade officials said several dozen could still be under the rubble.
"We haven't managed to find anyone alive yet, we found dead," Lukasz Kusion, a dog rescue team member told TVN24 television. "With every minute, chances are getting slimmer because of low temperatures," he said.
Prime Minister Kazimierz Marcinkiewicz told private Radio Zet he had seen the last person being brought out alive at 10 p.m. (2100 GMT) on Saturday.
As hearses drove up to the cordoned-off site to collect bodies, rescuers brought out cages of pigeons and rabbits from the rubble. Other pigeons flew aimlessly around the building.
Nolmans Francis was one of those that survived. The Belgian man works for the company Bricon, which makes devices for pigeons and had a booth at the exhibition. The booth was next to a hollow column holding up the roof; when it fell, Francis said he jumped inside the column.
"The roof fell on my head," he said. "I heard glass breaking. I saw the roof coming towards me like a wave ... it was over in 10 seconds." After he crawled out, he led rescuers back to his colleagues. All had only minor injuries.
Bitterly cold
Like Francis and his colleagues, many inside were able to escape, authorities said, but some escape routes may have been cut off. A government official noted that because the exhibition included carrier pigeons, some parts of the exhibition center were blocked off.
The cause of the collapse was not yet known. Some blamed heavy snow, but others wondered if the temperature difference between the heated exhibition center and the bitter cold outside could have weakened the structure.
It has been bitterly cold recently in Poland, with temperatures dipping as low as minus 25 degrees Celsius, or minus 13 degrees Fahrenheit.
Francis said an orchestra had begun playing loudly about half an hour before the collapse, and said perhaps the music contributed to the disaster.
After relatives and friends could no longer communicate with their buried loved ones by cell phone, there were feelings of pessimism, said Polish Radio Katowice reporter Anna Dudzinska after the incident Saturday.
"Now people are not so optimistic, I'm afraid," Dudzinska told CNN.
The cold posed a major problem. By early Sunday, temperatures had dropped to minus 17 degrees Celsius (1 degree F), and townspeople were bringing blankets to the disaster site, Dudzinska said.
A heated tent was set up near the rescue site, and heavy equipment was brought in to help stabilize the building's beams during the search. (Watch rescuers race against the cold -- 1:51)
Video of the scene showed piles of mangled steel beams and walls, apparently made from aluminum. Cages of live pigeons were in the wreckage.
"It looks like a collapsed house of cards," PolSat reporter Marek Sygacz told CNN.
Luckily, most visitors were gone when the collapse occurred, Francis said, adding that two hours previously, between 2,000 and 4,000 people were in the exhibition hall.
Earlier this month, heavy snow caused the roof of a German ice skating rink to collapse, killing 15 people.
