Officials say that two Polish coal miners remain unaccounted for and at least 10 have been injured after a powerful tremor shook the Rydultowy coal mine. Rescuers are struggling to reach dozens of others. The cause of the tremor was not immediately clear. The Polish Coal Mining Group says the accident took place Thursday morning. Officials say 68 miners were in the area at the time. They say 15 have been brought to the surface, including 10 who were hospitalized. Airborne ambulances are taking part in the rescue operation. Coal mine tremors can result from stress accumulated in the rock mass and can lead to dangerous rock bursts into the mine corridors.
