BOSTON (AP) -- A state social worker and the worker's supervisor have been fired as investigators try to determine what happened to a 5-year-old Fitchburg boy who hasn't been seen since September.
Department of Children and Families Commissioner Olga Roche said Tuesday the two employees, whose names were not disclosed, "have been terminated."
Investigators say Jeremiah Oliver was last seen by relatives Sept. 14 but police only learned recently that he was missing. A prosecutor is treating Jeremiah's disappearance as a possible homicide, and the boy's mother and her boyfriend have been charged in the investigation.
Roche called Jeremiah's disappearance a "deeply concerning case of neglect and abuse."
His family had been receiving services from the department since the fall of 2011 after the agency received a report of neglect.
In June, the social worker received a message from Jeremiah's day care indicating that his mother had said it was his last day and he would be leaving for Florida to live with his grandmother, officials said. But the social worker didn't confirm the information and also failed to conduct required checks, they said.
"This case represents a serious failure on the part of the social worker and supervisor assigned to the family," Roche said in a written statement. "The social worker assigned to this case did not conduct the required in-person, monthly checks on the family, as required by the Department; and the supervisor failed to enforce that policy."
She said the social worker's and the supervisor's other cases are currently under review and the department is working with State Police and prosecutors on the missing boy's case.
Jeremiah's mother Elsa Oliver, 28, was charged Monday with two counts of reckless endangerment of a child and two counts of being an accessory after the fact. A not guilty plea was entered on her behalf, and a judge ordered her to undergo a mental competency evaluation.
Oliver's boyfriend, Alberto Sierra, 22, pleaded not guilty after being charged with two counts of assault and battery with a dangerous weapon and two counts of assault and battery on a child. He is being held without bail pending a dangerousness hearing.
Oliver's two other children have been placed in the custody of the Department of Children and Families.