Eighteen miners are trapped in a Polish copper mine after an earthquake caused a tunnel collapse, the mine operator said Tuesday night.

Dariusz Wyborski, a spokesman for KGHM Polska Miedz SA, said the accident happened 600 meters (2,000 feet) below ground at the Rudna mine, in the southwestern region of Lower Silesia, Reuters reported.

He said the rescue operation was "difficult because huge amounts of rocks have to be removed."

There is no contact with the trapped miners because the 4.7 magnitude quake cut communication lines, the company added.

The mine has been in operation since 1974. KGHM is Europe's second-biggest copper producer.