A woman who lived with the mother of 23-month-old Brianna Blackmond when the girl was fatally injured in their home once had her four children taken from her and placed in foster care because of allegations of physical and emotional abuse, sources said yesterday.

The woman who was living with Brianna's mother was identified by sources yesterday as Angela T. O'Brien, 30. Sources say District police are examining the activities of everyone who may have had contact with Brianna before her death earlier this month, including O'Brien; Brianna's mother, Charrisise Blackmond; and Blackmond's unidentified boyfriend.

Brianna was killed less than two weeks after a D.C. judge ordered that she be taken out of foster care and returned to Blackmond, who during a trial a year earlier had been found neglectful of her eight children. Judge Evelyn E.C. Queen issued the order Dec. 23 after postponing a scheduled hearing on the matter and without seeing a report by the D.C. Child and Family Services Agency recommending that Brianna not be returned to Blackmond.

Although attorneys for Blackmond and Brianna agreed to the plan to return the girl to her mother, it is unclear whether anyone checked into the backgrounds of O'Brien and others who lived with or frequently visited Blackmond in her home on Bates Street NW.

In January 1998, O'Brien's four children were taken from her by D.C. social workers after one of them--a 2-year-old girl--was taken to Children's Hospital with a broken arm, sources said. Authorities were told that the girl had fallen off a bed, but medical reports suggested that the injury was inconsistent with that, the sources said.

O'Brien's children were returned to her in June, and she has since given birth to another baby. Because foster care records are sealed, the conditions under which the children were returned are unclear. Typically, parents in abuse cases may have their children returned after taking parenting classes or if there is difficulty in proving that the parents were the abusers.

Several efforts to reach O'Brien for a comment have been unsuccessful. Queen has repeatedly declined to comment on the case, as have officials at the Child and Family Services Agency, citing confidentiality policies. The attorneys for Blackmond and Brianna did not return calls requesting a comment; Queen has ordered them to be silent.

D.C. police, meanwhile, have not charged anyone in Brianna's slaying and say they are continuing to interview potential witnesses. Police officials say they eventually plan to take the case to a grand jury. Brianna's death has outraged child welfare advocates and put a spotlight on the already troubled Child and Family Services Agency, which for five years has operated under a court-appointed receiver because of widespread problems in the past.

Yesterday, two local members of Congress said they would ask the General Accounting Office to investigate the District's foster care system in light of the way Brianna's case was handled before her death.

"This case broke everyone's heart who read about it," said Rep. Thomas M. Davis III (R-Va.). Brianna's death, he said, "was something we don't ever want to see repeated in the city. This shouldn't happen anywhere."

During a Capitol Hill hearing on D.C. matters yesterday, Davis and Del. Eleanor Holmes Norton (D-D.C.) called for the GAO probe after Mayor Anthony A. Williams (D) was unable to answer Davis's questions about how Child and Family Services is faring under the receiver. Williams's role in the agency is limited because of the court oversight.

"One of the biggest problems is, I cannot reliably or confidently tell you whether we're better off or not" under the receiver, Williams told Davis.

In their testimony, and later in interviews, Williams and Alice M. Rivlin, chairman of the federally appointed D.C. financial control board, disagreed with the call for a GAO audit, saying the federal agency would produce a predictable report concluding that the D.C. foster care system has serious problems.

"The GAO would tell you there's a serious problem," said Rivlin, a former head of the congressional and White House budget offices. "We know that. We need to fix it."

Said Williams: "Alice is right. This is something we can do ourselves." But Davis and Norton said they would ask for a GAO report anyway.

The House's D.C. subcommittee devoted much of yesterday's hearing to what members called a lack of accountability in the city's foster care and mental retardation agencies.

Norton also called on Williams to set up a plan to audit every D.C. agency so that problems such as the government's failure to investigate the deaths of 116 mentally retarded residents in group homes does not And the mayor said he would ask the D.C. Council and Congress to set up an office of risk management that would identify serious problems such as the group home deaths and try to resolve them quickly before they spin out of control.

In calling for an agency-by-agency audit, Norton praised the actions taken by Williams concerning the mental retardation agency. Williams launched an investigation of the agency after the unexplained group home deaths were reported in The Washington Post; the probe has led to the firing or suspension of eight officials and prompted the mayor to temporarily turn over day-to-day management of the agency's cases to a nonprofit group.

"Mayor Williams deserves praise for conducting his own, no-holds-barred, objective audit," Norton said. "Its very usefulness, however, suggests that had there been in place a systematic plan for self-audits of every other agency, the District might have caught this tragedy before it reached 116 deaths."

Brianna's death has similarly focused fundamental questions on the city's child welfare system, which is responsible for protecting about 6,000 neglected and abused children in the District.

After Brianna was killed, all the other children in Blackmond's house, including two of Brianna's siblings and the O'Brien children, once again were taken away from their mothers by social workers.

Last week, O'Brien's attorney filed a motion requesting that O'Brien's children be returned to their mother, a source said yesterday. That case will be heard next week, a source said. O'Brien and Blackmond are godmothers to each other's children, the source said.

Ernestine F. Jones, the court-appointed receiver for Child and Family Services, yesterday broke her two-week public silence since Brianna's death. But she refused to discuss the circumstances surrounding Brianna's return to her mother and the role her agency played in it, citing confidentiality rules.

"I'm always troubled, to say the least, about any child dying, whether it is a child under our custody or not," Jones said. "This agency takes seriously its responsibilities to try and make sure that whenever children are placed . . . it is in the best interest of the child. We put safety first."

But when asked whether the child's safety and best interests were considered properly in Brianna's case, Jones said: "I don't want to make any comments about how this case was handled."

Staff writer Stephen C. Fehr contributed to this report.

CAPTION: Brianna Blackmond was 23 months old when she was killed this month.