Andrzej Gaska, a police spokesman, said many of the injured were being taken to three hospitals in the area. Some children were reported to be among the dead.
"The injured are being rushed by ambulance, police car and fire-brigade vehicles," he said.
Rescue workers used heaters to pump warm air into the ruin, fearing that many people would have been trapped without their winter coats and hats on.
Jaroslaw Wojtasik, a fire services spokesman, said that 117 people had been taken to hospitals with injuries and estimated that the rescue effort could take another 40 hours.
"We're going to keep our hope until the end," he said.
People trapped in the rubble called relatives or emergency services on their cell phones, telling them where they were, according to witnesses at the scene. Several foreigners were among the injured.
Those in the hall were attending a pigeon show on Saturday. The PAP news agency reported between 500 and 1000 people might have been in the hall.
Pictures from Polish television showed emergency workers shouting to each other and attempting to rescue people trapped under a collapsed corrugated metal roof. Pigeons escaped from broken cages walked around in the wreckage.
Kazimierz Marcinkiewicz, the Polish prime minister, flew in by helicopter and spent about 15 minutes looking over the site with rescue crews.
The 10,000-square-metre hall in the Bytkow district of the city had been hosting the pigeon exhibition, which opened on Friday.
The Pigeon 2006 fair was made up of more than 120 exhibitors, including groups from Belgium, the Netherlands,
Germany, Ukraine and Poland, according to the fair's website.
Poland is experiencing its coldest winter in several decades. The toll from a cold snap this winter stood at 199 on Saturday but was expected to top 200 over the weekend.