CHARLESTON, W.Va. -- Two teams of state, federal and Massey Energy officials went back into Massey Energy's Upper Big Branch Mine Wednesday afternoon after additional tests showed air quality was safe.The teams made an initial foray into the Raleigh County mine Wednesday morning, but made it only 1,000 feet before gas tests taken with handheld devices indicated elevated levels of carbon monoxide and methane.Crews are trying to examine Upper Big Branch and determine that the entire underground mine is safe for investigators to begin gathering evidence in their probe of the April 5 explosion that killed 29 miners and injured two others.The first trips back underground at Upper Big Branch were being made by specially trained rescue teams equipped with breathing apparatus. Since recovering bodies of the victims, officials have been kept out of the mine by poor air quality that raised concerns about a smoldering fire or follow-up explosions.
"Investigators won't go underground until the rescue teams complete their examination of the mine," said Amy Louviere, spokeswoman for the U.S. Mine Safety and Health Administration.But the initial rescue team efforts were also being stalled by Wednesday morning's bad air readings and by the fact that another borehole meant to help sweep fresh air into the mine had not yet been completed.Shortly before 10 a.m. Wednesday, one rescue team entered the mine's Ellis Portal and another the mine's North Portal, officials said. Both teams were forced to exit the mine within an hour when their handheld air monitors showed elevated levels of carbon monoxide and methane.Follow-up air samples, taking with more sophisticated equipment, showed the mine was safe for the rescue teams to re-enter by 3 p.m. Wednesday.Crews had hoped to go further into the mine, toward the longwall and mining sections where most of the victims' bodies were found. But until a last borehole is completed to ventilate the mine, they will be working only closer to the surface and will begin pumping water out of the mine.Investigators believe the explosion was caused by the ignition of methane gas and probably made far worse by a buildup of highly explosive coal dust. It was the worst U.S. coal-mining disaster in 40 years.Reach Ken Ward Jr. at firstname.lastname@example.org or 304-348-1702.