The death toll from a blast at a West Virginia coal mine rose to 25 on Tuesday, federal safety officials said, making it the worst mining accident in the United States in 25 years, according to a report by The New York Times.

The Times reports that four miners were still missing, and the officials said it was likely that those men also had been killed in the explosion on Monday.

A recovery operation was called off early Tuesday morning because high levels of methane gas made the mine unsafe for rescuers. Workers were boring holes into the mine to try to get more oxygen inside, an effort that was not expected to be completed for several hours.

To read the full New York Times report on this story, click here.

To watch a video produced by Discovery Channel that explains how miners work with sophisticated machinery to mine coal safely, click here.

To watch a video forum produced by the Commonwealth Club of California that discusses whether clean coal is the hope for the future, or just misleading marketing jargon, click here. Panelists weigh in on the possibilities and opportunities.