Felix G. Arroyo, City Hall’s chief of Health and Human Services, is under internal investigation for unspecified reasons, Mayor Martin J. Walsh confirmed yesterday.

“We have an internal investigation right now going on, into Felix,” Walsh told the Herald yesterday. Walsh declined to answer any questions about the nature of the probe or the reason for the focus on Arroyo. But Walsh said Arro­yo remains actively in his post and is not on leave.

“The situation is being investigated. When I have more information, I’ll be able to talk about it,” Walsh said.

Today, Walsh spokeswoman Nicole Caravella told the Herald that Arroyo is now on paid leave.

Multiple efforts to reach Arroyo for comment yesterday at home, by email and by phone were unsuccessful.

A reply email from his City Hall address yesterday had a subject line that read: “Vacation — Away from the Office.” The email then ­directed any inquiries to his office line.

Arroyo was a candidate in a crowded field who ran for mayor against Walsh in 2013.

Walsh then appointed Arroyo chief of Health and Human Services in January 2014. Prior to his appointment, Arroyo served as an at-large member of the City Council.

He was first elected in November 2009 and re-elected in 2011.

Arroyo’s biography on the City Hall website states: “Chief Arroyo has dedicated over a decade of his life to public service and community organizing. He worked to help pass the Affordable Care Act as the New England Field Director for Health Care for America Now and as an advocate for workers’ rights as the Political Director for SEIU Local 615. Chief Arroyo is a lifelong Bostonian and a graduate of the Boston Public Schools. He got his Bachelor’s degree in Human Services at University of Massachusetts Boston and his Master’s Degree in Community Economic Development at Southern New Hampshire University.”

Arroyo is the son of embattled Suffolk Register of Probate Felix D. Arroyo, who was elected to that position three years ago.

The elder Arroyo was suspended after court officials reported finding “serious deficiencies” in the way the probate and family court has been run under Arroyo. Earlier this year, Felix G. Arroyo donated $1,000 to his father’s campaign account.