WARSAW, Poland (AP) — Emergency crews in southern Poland worked Thursday to create underground conditions that would allow a search to resume for seven miners and rescue personnel who were missing after methane explosions in a coal mine killed five people.

The JSW company, which operates the Pniowek mine, said crews were building ventilation systems and pumping air into the search areas to lower the methane levels and the danger of further blasts.

The company said 25 people who were injured in the explosions remain hospitalized, nine of them in very serious condition at a hospital in Siemianowice Slaskie that specializes in treating mine accident victims, especially those with severe burns.

The first blast took place shortly after midnight Wednesday about 1,000 meters (3,000 feet) underground at the mine in Pawlowice, near the Czech border.

Three hours into the rescue operation, a larger, second blast occurred. Communications were lost with some of the rescuers, and the operation was suspended.

Members of 13 rescue teams waited Thursday to resume the search for the five rescuers and two miners were missing.

Poland relies on its own and imported coal for almost 70% of its energy, drawing criticism from the European Union and environmental organizations concerned about CO2 emissions and climate change.

Most coal mines are located in the southern Silesia region. Many are at risk of explosions from the sudden release of methane gas.

The Polish government has been actively scaling down the use of coal and recently announced it would end coal imports from Russia by May. The action is part of Poland’s drive to wean off dependence on Russian energy sources, but also comes in response to Moscow’s invasion of Ukraine.