No injuries have been reported.

Though investigators have not yet determined what happened at United Coal’s Pleasant Hill mine in Randolph County, local media speculation has hinted the blast may be related to a ferocious storm which ripped through the state in late June.

According to a report in West Virginia’s Charleston Gazette, although the incident occurred in a sealed underground tunnel, a lighting strike on metal within the mine could have caused the bursting of four water-trap pipes from newly constructed seals.

On June 29 a violent derecho which swept through much of region left Pleasant Hill and almost half a million West Virginians without power.

The Gazette said the blast caught the attention of MSHA because a lightning strike was initially presented as the “most likely” ignition source for the explosion that killed 12 miners at International Coal’s Sago mine in 2006.

In the report, Ed Peddicord, regional inspector-at-large for the state office of miners’ safety said the blown-out mine seal was built as recently as June 16 and that test results from June 24 showed it had cured to a strength standard set by MSHA following the Sago disaster.

When power was restored to the mine on June 1, two days after the storm had passed, officials of Pleasant Hill operator Carter Roag Coal investigated the area despite monitoring high levels of carbon monoxide.

Gas readings taken on site since the event indicate explosive levels of methane, high carbon monoxide and low oxygen – a mixture which has caused MSHA to prohibit anyone further from going underground.

Pleasant Hill made safety news last year when a former foreman, Luke W Pugh, was sentenced to a year imprisonment plus three years’ probation after admitting he lied about being qualified to conduct coal mine safety inspections.

MSHA said that on numerous occasions from June 2007 through August 2008, Pugh falsified the mine's pre-shift, on-shift, and daily report examination records by signing them as a certified mine examiner, knowing that he was not certified and using someone else’s certification number.

Pleasant Hill is located near the town of Mill Creek and produced 376,000 tons of metallurgical coal in 2010.