Nineteen Polish miners trapped 950 metres below ground by a cave-in at the copper giant KGHM’s Rudna mine in Polkowice, Lower Silesia, were freed early on Wednesday after a seven-hour rescue operation.

Forty two miners were working in the area when an around 10-second tremor measuring 5 on Richter scale took place late evening on Tuesday. Twenty two managed to leave the area by themselves, 19 were trapped by fallen rock.

The rescuers reached the miners after tunneling through huge rocks, KGHM spokesperson Dariusz Wyborski said.

"Eighteen of them were not injured," Wyborski said, adding that one of the miners required minor medical assistance.

Wyborski told PAP Polish news agency it was too early to estimate when production in the affected area can be resumed.

"Currently it is hard to say when extraction in the area of the cave-in will be resumed," Wyborski said. "In similar situations it can take from a few days to up to several months."