The death toll from accidents in recent days at two coal mines in southern Poland has increased to nine after four miners were brought to the surface and pronounced dead, authorities said Sunday.

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The miners were among 10 missing since an underground tremor and methane gas discharge at the Borynia-Zofiowka mine early Saturday. Six miners there remain missing, but there is no contact with them, and rescuers continue their search.

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At the nearby Pniowek mine, five workers died and seven are missing after repeated methane blasts that started Wednesday. The search for the missing there was suspended Friday after new explosions late Thursday injured 10 rescue workers, some seriously.

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Both mines are operated by the Jastrzebska Spolka Weglowa, or JSW, in the Jastrzebie-Zdroj region, close to the Czech border.

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The majority of Poland’s energy comes from coal, a proportion that is drawing criticism from the European Union and environmental groups who are concerned about CO2 emissions and meeting climate change goals. Most Polish coal mines are in the southern Silesia region. Many are characterised by the high presence of methane in the rock.

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Poland has been scaling down the use of coal and recently Prime Minister Mateusz Morawiecki ordered coal imports from Russia and its ally Belarus discontinued — in response to Moscow’s invasion of Ukraine, but also as part of Poland’s years-long drive to reduce its dependence on Russian energy sources.