The president and CEO of the University of Maryland Medical System resigned Friday amid an investigation into questionable business dealings involving board members, including Baltimore's embattled Democratic Mayor Catherine Pugh.

The resignation of Robert Chrencik came a day after the medical system received a subpoena for documents related to Pugh’s business dealings.

Chrencik -- who had led the medical system since 2008 -- had been on paid leave since March 25, the Baltimore Sun reported.

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“Today the Board of Directors and I received and accepted Chrencik’s resignation from UMMS, effective immediately. This action is an important step in moving the Health System forward during this critical time and we remain focused on delivering exceptional, safe, quality health care across Maryland," acting CEO John W. Ashworth said in a statement before thanking him for his 35 years of employment at UMMS.

The medical system has been under intense pressure since a Sun investigation revealed nine of its board members have business deals with UMMS worth hundreds of thousands to millions of dollars each.

Chrencik previously opposed a proposal to bar board members from entering into lucrative no-bid contracts with the hospitals they oversee, according to the paper.

Pugh, 69, is facing calls to step down after accusations that she sold $500,000 worth of her self-published “Healthy Holly” illustrated children's books to the medical system.

UMMS reportedly paid for 100,000 copies of the book between 2011 and 2018. Chrencik acknowledged there was no competitive process for purchasing the books.

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Pugh apologized for the deal. Her attorney on Thursday said the calls for resignation have “not fallen on deaf ears,” the Washington Post reported.

“In the near future, she will make a decision that is in the best interests of Baltimore,” attorney Steve D. Silverman said.

State Sen. President Thomas Mike Miller, a Democrat, previously demanded Chrencik and the board Stephen A. Burch attend a closed-door meeting to answer questions about the deal.

“The governor wanted to press that issue very strongly,” Miller said. “I asked the question also: ‘Why did it continue? ‘They said, ‘She continued to write more books.’ They didn't tell us who authorized the check, who signed the check and who approved the deal.”

Federal agents on Thursday searched Pugh’s two Baltimore homes, her City Hall office and a nonprofit she once led. Pugh resigned from the board and has taken an indefinite leave of absence from her office.

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Maryland Gov. Larry Hogan, a Republican, encouraged Pugh to step down after the early morning raids.

“Now more than ever, Baltimore City needs strong and responsible leadership. Mayor Pugh has lost the public trust,” he said. “She is clearly not fit to lead. For the good of the city, Mayor Pugh must resign.”

State lawmakers passed legislation this year to dissolve the UMMS board in several stages. Members would be required to reapply and members would be barred from holding single-source contracts with the system.