(CNN) House Democrats are asking Monday to subpoena records that they think will show that Environmental Protection Agency Administrator Scott Pruitt used his staff to run personal errands, including trying to buy a used mattress from the Trump International Hotel in Washington during his controversial apartment search.

In an interview with House Oversight Committee members, one of Pruitt's top staffers who describes herself as a personal friend of Pruitt, Millan Hupp, told investigators that she searched for rental properties for Pruitt and his wife for several hours a week over the course of several months, touring more than 10 of those properties during work hours.

Hupp, who works as a scheduler at EPA, said it was mostly on her lunch break, which she felt was appropriate, but Democrats on the committee are alleging it's a violation of rules that prevent federal employees using public office for private gain. They're asking Oversight Committee Chairman Trey Gowdy, a South Carolina Republican, to issue subpoenas for communications related to her work.

When asked about the letter, EPA spokesman Jahan Wilcox said, "We are working diligently with Chairman Gowdy and are in full cooperation in providing the Committee with the necessary documents, travel vouchers, receipts and witnesses to his inquiries."

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