After a bitterly cold night when temperatures plummeted to minus 17 degrees Celsius (1.4 degrees Farenheit), cries emerging from the twisted sheet-metal wreckage died into silence as victims lost their battles for survival.

Some trapped victims had called loved ones on their mobile phones from the ruins of the hall in this southern town, describing the frozen corpses around them and the metal sheets that boxed them in during their last moments alive.

One victim, Tomek Michalski, called his mother in tears late Saturday from within the rubble.

"Both of his legs and his shoulder are blocked by metal bars," she said. "Next to him, a young woman is dead. He tried to save her life. She was a colleague. She had a six-month-old boy."

National fire chief Kazimierz Krzowski declared an end to the rescue operation late Sunday morning. "The rescue phase of the operation is over. The chances of finding a survivor are close to nought," he said.

The last survivor to be pulled from the wreckage was found at 10:00 pm (2100 GMT) on Saturday night, and medical experts helping with the rescue effort said it was unlikely anyone could have survived overnight beneath the frozen metal.

Marek Brodzki, a surgeon in charge of an 18-person medical team at the site, said the metal of the building's remains, covered in snow, had acted like a freezer.

"The rescuers are cutting into the sheet metal, boring holes into it. But inside it's even colder," he said.

"Now I'm just identifying the bodies," Brodzki said.

At least 200 people were attending the racing pigeon exhibition when the roof fell. Some 141 people were injured, including 100 Belgians and dozens of other foreigners, according to various sources.

"We heard a terrible noise and then the whole roof collapsed," 60-year-old Belgian vet Henk Weerde told AFP as rescue workers led him to an ambulance, his head covered in blood.

Specialised mining teams, used to operating in pitch black, had worked alongside police specialists and sniffer dogs in the desperate search for the living.

Priests were also on hand in this overwhelmingly Catholic country, to administer the last rites.

President Lech Kaczynski declared three days of national mourning starting Sunday afternoon. "It is the biggest catastrophe in democratic Poland," he said, confirming that 66 people had been killed inlcuding two children.

One survivor, speaking by telephone from his hospital bed, said the building crumpled in a moment.

"It all happened so fast, in three seconds," he said.

"If the roof had collapsed an hour earlier there would have been a massacre," he said. "The exhibition hall was packed at the time. There were so many people you couldn't move."

Police said the hall could hold 700 people but the crowds had dwindled before the disaster struck.

Four foreigners were among the dead, from Germany, Belgium, the Czech Republic and Slovakia, police said. The bodies of six victims still needed to be identified.

French President Jacques Chirac, German Chancellor Angela Merkel and Russian President Vladimir Putin offered their condolences in separate statements Sunday as the Polish government struggled to come to terms with what happened.

Prime Minister Kazimierz Marcinkiewicz, who interrupted a skiing holiday to visit the scene, ordered an investigation amid suggestions that too much snow had been allowed to accumulate on the five-year-old roof.

The government also ordered local authorities to clear snow from all buildings open to the public.

An AFP reporter at the scene said he had seen a metre (three feet) of ice on the pieces of roof which had hit the ground. Interior Minister Jerzy Polaczek said the layer was half that thick at 50 centimetres.

Chorzow fire brigade spokesman Janusz Jonczyk said heavy snow on the roof appeared to have caused the collapse. But a spokesman for the building's management company said snowfall was regularly removed.

The only survivors seen on Sunday were the pigeons, their plumage matted and ragged. Rescue workers slipping on the icy metal sheeting carried the birds out in the cages which, along with their feathers, had saved their lives.

Less than a month ago, a similar tragedy occurred in Germany when the roof of a skating rink in Reichenhall collapsed under the weight of snow, killing 15 people.

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