On Sunday, a day after the roof caved in during an international racing pigeon show, authorities were turning their attention to demolishing the rest of the building, whose collapse left 160 people injured.
Krzysztof Mejer, a spokesman for the government of the Silesia region, said: "The rescue operation is over."
Thirteen rescue dogs from Poland and the neighbouring Czech Republic indicated that there were no more bodies in the debris, he said.
"We can confirm 66 people were killed and we don't expect anyone else to be found under the wreckage."
The building collapsed on Saturday afternoon with an estimated 500 people inside. The last person rescued alive from the building was pulled out less than five hours later, and extreme cold of minus 17C (1F) set in overnight.
Rescue crews had used hand tools to carve through the sheet metal and snarled poles of the collapsed building so as not to risk harming any potential survivors.
On Sunday, Kazimierz Krzowski, the fire chief, said that heavy machinery was now being called in to tear down the rest of the building.
He said: "The parts of the structure that are not lying on the ground are a threat."
There was little sign of activity at the site Sunday evening, and lights were turned off.
Police initially said snow caused the roof collapse. Jerzy Polacek, the transport minister told TVN24 television that there was about half a metre of icy snow on top of it at the time.
However, Bruce Robinson the president of the Katowice company that organised the fair, said that "the reasons are not clear" and that the firm was working with authorities to help determine them.
Grzegorz Slyszyk, a lawyer for the building's owners, said snow had been cleared regularly from the roof. He said they had heard from a Belgian witness that the floor collapsed before the roof did - raising the possibility of subsidence.
Faulty building materials could
have caused the building collapse
Other potential causes to be investigated include the possibility that faulty building materials were used and "how the materials reacted over time" to the contrast between bitterly cold temperatures outside and warm ones inside the building, Slyszyk said.
Tadeusz Dlugosz, a survivor of the collapse, was still at the site on Sunday morning, seeking information on where the body of his 26-year-old son had been taken.
Dlugosz said: "It was his idea to come to the fair ... and he found his grave there. During the fair he was wearing only a sweater. That could be the cause of his death.
Crumpled bird cages were scattered inside the building near the entrance, and white and brown pigeons perched on the twisted rafters.
Tomasz Bajor, the city's spokesman, said that some of the birds were able to flee their cages when they were broken, while others were recovered from their cages.
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.
Authorities say of the 66 dead,
seven were foreigners
Polish authorities said 51 of the victims had been identified by Sunday afternoon, including seven foreigners - two Slovaks, two Czechs and one victim each from the Netherlands, Belgium and Germany.
The Foreign Ministry in Berlin said two Germans were killed.
Lech Kaczynski, the Polish president, declared a national period of mourning that will continue until Wednesday.
Visiting the scene of the accident, Kaczynski described it as "the greatest tragedy" to hit post-communist Poland.