NASHVILLE — The head of Tennessee’s child welfare agency resigned Tuesday under scrutiny over how her agency handled the cases of children who were investigated as possible victims of abuse and neglect, then later died.

Governor Bill Haslam announced Kate O’Day’s resignation as Department of Children’s Services commissioner, saying, ‘‘She was concerned that she had become more of a focus than the children the department serves.’’

Last week the governor was defending O’Day’s leadership, even after the agency told a federal judge it could not say with certainty how many children died while in its custody.

‘‘She has done a lot of good work in identifying longstanding problems that have hampered the department, and we will build on those efforts as we move forward,’’ the governor’s statement said. Neither he nor O’Day were answering questions Tuesday about the latest developments.

O’Day, 56, had a troubled tenure, but the agency’s problems predated her. The agency has been under federal court oversight for more than a decade because of problems with Tennessee’s foster care system.