Washington (CNN) -- Protesters wearing surgical masks on Wednesday interrupted a congressional hearing on the coal industry.
The three protesters stood up in the Select Committee on Energy Independence and Global Warming hearing while Gregory Boyce, Peabody Energy Corporation's president and chief executive officer, was testifying.
They stood silently, extending their hands, which were stained with what appeared to be coal dust. At one point, they put a piece of coal on the desk where Boyce and other coal industry executives were sitting.
The protesters' masks were covered with writing.
The coal industry executives are answering questions about climate change and other challenges facing their industry.
The hearing comes more than a week after an explosion at a West Virginia mine killed 29 miners. The last of the bodies from Massey Energy's Upper Big Branch mine were recovered Tuesday.
The CEO of Massey Energy, Don Blankenship, was not among the executives testifying Wednesday.