Pawel Markowski said that a doctor confirmed the death of a miner that the rescuers reached on Wednesday. He added that the rescuers can see another missing miner but have not been able to contact him. The unreachable miner is allegedly under a massive rock that the rescuers will need to lift or crush.
Prime Minister Beata Szydlo was to come to the mine later Wednesday, officials said.
The tremor occurred shortly after 9 PM. Tuesday some 1,100 meters underground in the Rudna mine, in Polkowice, in the southwest.
The German Research Center for Geosciences in Potsdam, near Berlin, reported a 4.5 magnitude shallow earthquake in the region at the time of the cave-in.
Jolanta Piatek, spokeswoman for the KGHM Polska Miedz, or Polish Copper, mining corporation, said that the body of the second fatality was also found underground. Earlier, one of nine miners brought to the surface shortly after the cave-in had also died.
Five others have been hospitalised but their lives are not in danger. Nine rescue teams continue the search for those still missing. The cave-in was in the heavy machinery area.
The rescuers are receiving signals from the locators of the missing miners, but have had no direct contact with them, Piatek told The Associated Press.
Work continues as usual in other areas of the mine, Piatek said.
Known as the Polish State Mining and Metallurgical Combine under communism, KGHM went through restructuring and partial privatisation in 1991 as Poland shifted to a market economy. It has grown to be one of the world's major copper and silver producers. It also has mines in Chile, Canada and the United States.