An earthquake has left at least four people dead and four others missing at a copper mine in Poland, owners KGHM said Wednesday.

Four bodies were recovered at a depth of about 1,100 meters (3,600 feet) in the Rudna mine in the southwestern town of Polkowice, the head of the mine, Pawel Markowski said.

He said the four missing are likely buried a dozen or so meters away from the rescuers, who have been slowed down by having to clear away large rocks by hand.

Five workers sustained minor injuries. Two of them were hospitalized but doctors said their lives were not in danger and they would be released within days.

The US Geological Survey said the magnitude 4.4 quake struck deep underground on Tuesday evening near the town of Glogow.

The mine’s managers estimated the energy released by the quake at eight points on a scale of 10 used by the mining industry.

One of the largest copper mines in the world, Rudna has 11 operating shafts at a depth of around one kilometer.

It employs 4,400 people and extracts around 12 million tones of minerals a year.

Prime Minister Beata Szydlo cancelled a cabinet meeting scheduled early Wednesday in order to travel to the site.

Source: AFP