(CNN) Democratic Baltimore Mayor Catherine Pugh will be taking an "indefinite leave of absence," her office announced Monday, citing a battle with pneumonia. The announcement comes at the same time she's facing a scandal over a major purchase of children's books she authored by the University of Maryland Medical System and other groups.

"She has been advised by her physicians that she needs to take time to recover and focus on her health," a statement from Pugh's office read, adding that, "with the Mayor's health deteriorating, she feels as though she is unable to fulfill her obligations as Mayor of Baltimore City."

The announcement came the same day Maryland Republican Gov. Larry Hogan wrote to the Office of the State Prosecutor requesting an investigation into the sales of thousands of Pugh's book, "Healthy Holly," to the University of Maryland Medical System while she was a member of its board.

"All Marylanders have an expectation that their public officials as well as individuals involved with institutions that are funded by and closely related to the State, will follow the highest legal and ethical standards," Hogan wrote in a letter obtained by CNN.

CNN has reached out to the Office of the State Prosecutor and Pugh's office for comment.

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