(CNN) Two of Environmental Protection Agency Administrator Scott Pruitt's closest aides at the agency resigned on Wednesday, an EPA official confirms to CNN.

Sarah Greenwalt, a senior counselor to Pruitt, and Millan Hupp, who worked as Pruitt's scheduling director, both resigned on Wednesday, the official told CNN. Their resignations are set to take effect late this week and early next week, the source said.

Hupp recently testified before the House oversight committee that she did many personal tasks for Pruitt, including house-hunting and inquiring about obtaining a used Trump hotel mattress.

Their resignations leave Pruitt increasingly isolated at the EPA, where he has lost the confidence of most of the agency's career staff and many conservative political appointees who feel that Pruitt's ethical lapses have done a disservice to the President's agenda.

Still, Pruitt earned President Donald Trump's praise earlier Wednesday.

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