Investigators haven’t yet stepped into the Upper Big Branch Mine in Southern West Virginia -- the site of this month’s explosion that killed 29 miners -- but
“„Air samples did not show high levels of explosive gases just before an explosion in a West Virginia coal mine that killed 29 workers, and what caused the disaster remains unknown, the mine’s owner said Monday.
“„Massey Energy Co. board director Stanley Suboleski said the samples were taken by a foreman as part of a shift change exam of the mine, just “tens of minutes” before the blast. The examination also showed that air flow in the Upper Big Branch mine was fine.