The FBI has entered the probe of Assisi Inc., the nonprofit shelter for battered women in Prince George's County already under scrutiny by county officials for its handling of a $111,000 federal grant.

The federal probe centers on allegatins that Assisi officials failed to pay U.S. and state taxes for the shelter, using the money instead for inappropriate purposes such as salaries and personal expenses, sources said.

FBI officials would not confirm the existence of the federal inquiry, but the sources said it has been under way for two months.

The FBI's probe parallels a similiar examination of Assisi by the Prince George's County government, which is responsible for administering the federal funds used to operate the shelter near Upper Marlboro.

The county is examining Assisi's alleged failure to return employe withholding taxes to the government, offer many of the social services and programs for which it received federal funding and account for money collected and used.

While the probe is proceeding, the county has held up further payments to Assisi of the $111,000 grant under the Comprehensive Employment and Training Act (CETA), a federal manpower program. The shelter already has been paid about $48,000 of the grant.

Assisi also supports itself through private donations and about $15,000 in grants from philanthropic organizations.

Located on 68 acres of rolling countryside, Assisi is the county's only home for battered women. Since it began 21 months ago, the shelter has been run by Elizabeth Fischer, who has said she came to Washington several years ago as a destitute woman from her home in North Carolina.

Fischer was unavailable yesterday for comment on the FBI probe but said recently that the shelter was "having growing pains. We're going from a volunteer organization to a funded organization. We've been playing catch-up with the books."

In addition to Fischer, the shelter gets its overall policy direction from a board of directors that includes some of the most prominent politicians and civic leaders in the county.

William E. Knight, a lawyer who is vice chairman of Assisi's board, said yesterday that any discrepancies in the organization's finances were inadvertent. "When they check the records, it's not a pretty sight from an accounting standpoint, but there was no criminal conduct or intent," he said.

Board Chairman Liane Gonzales reacted angrily yesterday to reports of the FBI investigation. "As far as I'm concerned that's all rumors. It's really great to report rumors," she said.

Although FBI officials will not discuss the matter, the agency apparently began looking into Assisi's financial affairs after several employes asserted that the shelter's accounting books were being kept improperly, and that several thousand dollars in payroll taxes were not being paid despite the withholding of moneys from employe paychecks.

Fischer has said the charges were fabrications by disgruntled employes. She attributes the condition of the Assisi books to inexperienced bookkeeping.

Since the allegations first surfaced a few months ago, the FBI has contacted several persons connected with Assisi, The Washington Post has learned.

Several employes also have contacted county officials with claims that Assisi, despite receiving the federal and other grants, is not offering many services that it claims to offer.In particular, they say it does not offer a 24-hour hot line, regular therapy for children or battered women, programs for chronic abusers, and 11 auxiliary shelters, which Fischer has publicity said exist at Assisi.

Employes and former residents have also said that residents frequently must pay for their food and shelter and that donations of furniture and clothing made to the shelter have at times been taken by staff members for personal use, sources said.