The U.S. Justice Department has begun a special probe into the quality of care at District government-funded facilities for the mentally retarded.

The inquiry, by the department's Civil Rights Division, was sparked by an investigation by The Washington Post published in March that found 350 documented cases of abuse and neglect as well as profiteering in the city's 150 taxpayer-financed group homes for the retarded.

"We take all allegations of abuse and neglect very seriously and certainly follow up to determine whether allegations warrant additional federal action," said Bill Lann Lee, acting assistant attorney general for civil rights. "That's what we're doing in this case."

Lee has commissioned Tony Records, a nationally known expert on services for the retarded, to help with the division's investigation.

In recent weeks, the Justice investigators have gone into about a dozen group homes across the Dis trict, including homes run by the city's largest service providers, Voca and D.C. Family Services. Investigators plan to visit a broad cross section of the city's homes and day programs in the weeks ahead, interviewing nearly 100 retarded residents and scouring their medical and treatment records.

As a party to Evans v. Washington, a 23-year-old federal lawsuit that helped deinstitutionalize the District's mentally retarded population, the Civil Rights Division periodically has taken actions to prod the District toward better services. "But I don't think we've ever looked at this many homes this quickly," said a Justice official involved in the case, citing a "sense of urgency" regarding the allegations.

The civil rights inquiry into the District's system is relatively unusual in its focus: examining the treatment of retarded people in community-based settings that have become a central component of reform efforts across America, not in the large asylums upon which Justice attorneys have concentrated their legal efforts in recent decades.

Justice undertakes the inquiry in the District in its capacity as a "plaintiff-intervenor" in the still-open Evans case, whose consent decrees are supposed to offer special protection to the retarded men and women who were moved from a troubled city-run asylum in Laurel into smaller facilities in the District. Results of the new investigation are expected by June. Justice may use the findings to press for remedies through the ongoing federal court case or other means.

In a separate criminal investigation, the FBI's Washington field office is examining allegations of corruption and Medicaid fraud against several providers of services to the District's retarded. An FBI spokesman declined to comment on the investigation.

The District's taxpayer-funded programs for the retarded are among the most expensive in the country, with an average cost per patient of more than $ 100,000 a year. The Washington Post found that, with minimal oversight by city agencies and the D.C. Council, the care of the retarded and millions of dollars in public funds had been entrusted to a convicted embezzler, a nightclub owner and several companies with long histories of abusing or neglecting their wards. Documented abuse went unpunished: From 1990 to 1999, the city failed to issue a single fine against a company found to have mistreated a retarded person. And 50 deaths in the last three years went unexamined by city officials.

On Sunday, another retarded person in the District's care, Desmond Brown, 39, died at Providence Hospital. He was sent to Providence's intensive-care unit after developing an advanced case of pneumonia at a network of for-profit group homes repeatedly cited for medical neglect.

Justice Department intervention was instrumental in building the District's current privatized, community-based system.

In the 1970s, the Civil Rights Division joined a federal lawsuit filed by parents of retarded men and women housed at the District-run asylum called Forest Haven in Laurel; the division's subsequent documentation of Forest Haven's poor medical treatment helped force its closing in 1991. The transfer of residents to group homes and treatment programs within the District was considered a historic reform effort at the time, as the city's retarded population became one of the most deinstitutionalized in the country.

Jearline F. Williams, director of the D.C. Department of Human Services, which oversees care for the retarded, said her agency welcomed the civil rights and FBI investigations and was cooperating fully with Justice officials. After The Post's series, Williams joined D.C. Mayor Anthony A. Williams (D) in ordering the immediate closure of two homes and a farm-labor program whose poor conditions and abused residents had been featured in the series. She also removed the chief of the Mental Retardation and Developmental Disabilities Administration, which has direct responsibility for group home oversight, and requested the aid of the U.S. Department of Health and Human Services in accelerating reform.

Of her department's "massive overhaul" of its services to the retarded, Williams said, "We've got a lot of partners in this, from the community and from the federal government. I see real change ahead."