A spokeswoman for a Polish mining corporation says that one miner has died and seven are missing underground following a strong tremor that caused a cave-in at a copper mine in southwestern Poland.

Jolanta Piatek, spokeswoman for the KGHM Polska Miedz mining corporation, said that the tremor occurred shortly after 9 p.m. Tuesday some 1,100 meters (3.610 feet) underground in the Rudna mine, in Polkowice. Some 16 miners were in the area, she said. Nine of them were brought to the surface and hospitalized with injuries — one of whom died.

Piatek said three teams of rescuers were searching for the missing miners at the cave-in area.

KGHM has now lost seven miners this year in accidents in its mines.