BOSTON — The heavy caseload at a regional office of the state Department of Children and Families does not excuse the failure to properly monitor a 5-year-old boy who has not been seen in months and is feared dead, according to a report issued Thursday by the state Office of the Child Advocate.

The workload provided a context but not an explanation or excuse for failures in basic protective care and supervision in the case of Jeremiah Oliver of Fitchburg and his family, said Child Advocate Gail Garinger.

The report was issued as two legislative committees held a hearing prompted by the boy’s disappearance.

“The department lost track of a kid,” said state Rep. David Linsky, chairman of the House Post Audit and Oversight Committee. “That’s absolutely inexcusable.”

Linsky asked DCF Commissioner Olga Roche, who testified for more than three hours before lawmakers, if she was 100 percent confident that no other children in the system were currently unaccounted for.

Roche replied that she was, noting the department fired the social worker assigned to the Oliver family for failing to make required monthly visits to the family, and also terminated the social worker’s supervisor and an area manager.

Roche said the agency immediately made visits to all other children assigned to the social worker to assure they were safe, and ordered checks on all children 5 years old or younger whose families were under DCF supervision.

“This was a unique circumstance of a social worker, a supervisor and a manager who failed to do their duties,” Roche said, adding that the agency serves more than 100,000 children a year and most do well because of the dedication and commitment of social workers.

Linsky, a Natick Democrat, agreed, but added:

“In this type of situation we can’t afford to get it right 99.9 percent of the time. We have to get it right 100 percent of the time.”

The department has been working since 1986 under a maximum caseload ratio of 18 families, and no more than 30 children, per social worker, officials said. The ratio is weighted to give a higher value to more difficult cases.

A $9.2 million increase in funding for the agency requested Wednesday by Gov. Deval Patrick would help lower the caseload ratio to 15-to-1, with a maximum of 28 children, Roche said, in keeping with an agreement reached last year with a union representing social workers.

The union contends that many workers have caseloads that exceed guidelines, but the caseload of the social worker assigned to the Oliver family was not above the current limit, Roche told lawmakers.

Garinger, in her report, said the social worker, whose name has not been released, made only two monthly visits to the home after the family moved to Fitchburg last January and the case transferred to the North Central regional office.

The last visit came in April, despite subsequent reports of abuse and neglect that were filed by mandated reporters outside of the agency.

“Everyone at DCF agrees that the most basic obligation of front-line social workers is to ‘visit your children,”’ Garinger said in a statement. “This is the cornerstone of protective work but did not happen with Jeremiah Oliver.”

According to the report, there was no meeting or telephone call between the two regional offices when the case was transferred, and Massachusetts never received information it requested about “serious child protective concerns” in another state where the family had lived prior to 2011.

In addition to the report by the Child Advocate and an earlier internal investigation by DCF, Gov. Patrick has requested an independent review of the agency by the Child Welfare League of America.

Jeremiah’s mother, Elsa Oliver, and her boyfriend, Alberto Sierra Jr., have pleaded not guilty to child endangerment and abuse charges in connection with the alleged abuse of Jeremiah’s 9-year-old brother and 7-year-old sister, who were placed in state custody.