Massey Mine Investigation

Officials from the Mine Safety and Health Administration illustrated their working theory on what caused the Upper Big Branch mine explosion in West Virginia last April.

Nine months after the deadly coal mine explosion in West Virginia, federal investigators have revealed their working theory about the cause. It directs blame toward a series of maintenance and equipment failures at the Upper Big Branch mine.

NPR News has learned that safety systems were not working properly before that blast at the Upper Big Branch coal mine. Some mine safety experts believe these water-based safety systems might have helped prevent the blast if they all had been working together properly. Host Scott Simon speaks with NPR's Howard Berkes about new developments in the investigation of last year's coal mine explosion.

NPR NEWS INVESTIGATION: Legally required water systems at Massey Energy's Upper Big Branch coal mine in West Virginia were not functioning properly before the April 5 explosion that killed 29 mine workers. Some experts say these systems might have helped prevent the disaster if they had been working properly.