It's been more than two months since that explosion killed 29 men, and we may be one step closer to knowing the cause.
Richmond-based Massey Energy says exploratory teams found a crack in the mine's floor. It's that crack that could have allowed methane gas through the floor.
Massey says the new crack was found last week near the longwall machine. That device has large shields that support the roof and protect the miners during mining. However, the teams could not determine whether it was the source of the explosion.