The DEP, which issued the order on Friday, said the spill was the second in three weeks from the longwall operation. The Charleston Gazette said Independence Coal was unaware of the spill until DEP inspectors arrived.

It is not known how large the spill is, however no public water supplies have been threatened and there was no evidence of a fish kill.

A DEP spokesperson told the Charleston Gazzette that the mine had experienced spills because of the large amount of water used underground to suppress dust and methane gas liberated by the longwall operation.

The most recent spillage resulted from a settling pond, which had been shut down for cleaning. During the night the pipe opened releasing the black water into the river.

The Charleston Gazzette said Massey was still investigating how the valves were opened.