Michigan Gov. Gretchen Whitmer's health department director is set to receive a $155,506 payout after his sudden resignation in January, and his departure still has not been explained, The Detroit News first reported on Monday.

Former Michigan state health department director Robert Gordon also signed a confidentiality agreement "in the interest of protecting deliberations among government officials," according to the deal obtained via an open-records request by The Detroit News.

"In response to any inquiries from prospective employers, employer will state that employee voluntarily resigned," the agreement read, according to The Detroit News' reporting.

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A source close to Republican leadership in the state told Fox News an investigation could be announced as early as Tuesday. 

Republicans were quick to seize on the report.

Michigan Gov. Gretchen Whitmer at a roundtable discussion on health care last October.

Michigan Gov. Gretchen Whitmer at a roundtable discussion on health care last October. (Nicole Hester/Ann Arbor News via AP, File)

"We're still investigating the things the Whitmer Administration has done during COVID in plain sight, when we find out about a secret payoff behind closed doors," state Rep. Steve Johnson, chair of the Michigan House Oversight Committee, told Fox News in a statement. "While it doesn't surprise me, the deception is shocking and shows how badly this Administration needs oversight so they can be held to account."

"Mr. Robert Gordon was the state's health director and played an instrumental role in the state's COVID-19 response," Ted Goodman, spokesman for the Michigan GOP, told Fox News in a statement. "Michigan taxpayers deserve to know the circumstances surrounding the resignation of Mr. Gordon in the middle of a public health crisis. Why is Gov. Whitmer refusing to explain this secret deal?"

Robert Gordon in an undated photo.

Robert Gordon in an undated photo. (Michigan Executive Office of the Governor, File)

The Detroit News also reported that Mark Totten, the governor's chief legal counsel, sent Gordon an email accepting his resignation 11 minutes before Gordon announced his resignation via social media.

Dennis Muchmore, former Michigan Gov. Rick Snyder's ex-aide, told The Detroit News he could not remember a separation from that administration that had "cash involved."

"Sometimes, we would give them a couple of weeks of vacation at the end, but most all of the ones I can remember always had time coming to them," Muchmore told The Detroit News. "I don’t know of any cash involved."

Whitmer previously dodged a question about whether she was behind Gordon's departure.

"To lead this department in unimaginable circumstances, it has been grueling," Whitmer said at a Jan. 25 press conference according to The Detroit News. "On behalf of all of the people of Michigan, I want to thank him for his service to our state. He worked hard to protect our public health."

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The Detroit News' report comes as Republican state legislators in Michigan have Whitmer in their sights. They recently called for an investigation into the governor’s handling of nursing homes and other long-term care facilities during the coronavirus pandemic.

Fox News' inquiry to Whitmer was not immediately returned.

Fox News' Houston Keene contributed to this report.