House Oversight and Government Reform Committee Chairman Trey Gowdy (R-S.C.) has begun probing Environmental Protection Agency Administrator Scott Pruitt's $50-a-night housing arrangement on Capitol Hill, a GOP source told The Hill Friday night.

The investigation adds to a growing controversy surrounding Pruitt, who already faces some calls to resign from both sides of the aisle.

The Oversight and Government Reform Committee "has been looking into Pruitt's condo deal," a Gowdy aide said. "The EPA produced documents to the Committee this week, including both the March 30 and April 4 memos."

The pair of internal memos were written by Kevin Minoli, the EPA's designated ethics official. In the first memo, Minoli concluded that Pruitt's $50-a-night lease with co-owner Vicki Hart - the wife of an energy lobbyist - did not violate federal gift rules.

But just days later, on Wednesday, Minoli wrote in another memo that he made that conclusion without having all the facts.

"Some have raised questions whether the actual use of the space was consistent with the terms of the lease," Minoli wrote, according to The Washington Post. "Evaluating those questions would have required factual information that was not before us and the review does not address those questions."

Gowdy has been under mounting pressure to step up his investigation into Pruitt, who's faced a barrage of negative headlines in recent weeks related to his living arrangements and spending on private jets, office furniture and a security detail.

Pruitt has maintained the lease followed ethics requirements and that his spending is not excessive.

In February, Gowdy began investigating Pruitt over numerous first-class flights funded by taxpayers. But so far, the retiring GOP chairman has not acted on calls by his Democratic counterpart, Rep. Elijah Cummings of Maryland, to bring Pruitt before his committee to personally answer lawmakers' questions.

Dozens of Democrats on Friday called for Pruitt to resign or be fired. Three House Republicans - Reps. Ileana Ros-Lehtinen (R-Fla.), Carlos Curbelo (R-Fla.) and Elise Stefanik (R-N.Y.) - also have called for Pruitt's ouster.

President Trump has indicated support for Pruitt, but noted this week he would be looking into the mounting accusations against him.