The FBI is investigating allegations of financial impropriety at the University of the District of Columbia, including the handling of rental payments from businesses with stores located on UDC-controlled properties, according to two sources knowledgeable about the probe.

UDC President Julius F. Nimmons Jr. said yesterday that the FBI had not informed him of an investigation, first reported by the Washington Times. Nimmons also said he was unaware of any problems at the school, the District's only public institution of higher education, that were serious enough to warrant an FBI probe.

"If there is something wrong that I have not uncovered or discovered or attempted to address and somebody knows it, I wish they would come let me know so I can deal with it first," an angry Nimmons said.

Sources said FBI agents are interviewing people knowledgeable about UDC officials' handling of school finances and are asking about a variety of issues. Among other things, the questioning has dealt with some of the issues probed last year by the D.C. inspector general's office concerning allegations that tens of thousands of dollars were mishandled by UDC.

For example, the inspector general's office looked into allegations that receipts from money collected in the UDC parking garage did not match parking deposits made into a school account. Last month, a UDC employee was convicted of stealing $69,000 in parking revenue and sentenced to eight months in a halfway house.

The FBI is examining whether the school mishandled the collection of rental payments from businesses that operate on its main campus on Connecticut Avenue in Northwest Washington. FBI investigators also are collecting information about a situation last year in UDC's Continuing Education Department, where teachers had not been paid regularly because funds meant for their salaries had been spent on other things.

One source said that past chief financial officers at UDC have told top school officials for years that there were problems with collecting rental money from various sources.

In the case of one business, the source said, no money was received from the business at all, and in other cases, only half the rent was ever marked on the books as being paid. Attorneys working for the school were notified, but nothing was ever resolved, and the problems still exist, the source said.

The FBI probe comes at a time when UDC officials are hoping to stabilize the school after years of turmoil. The 1990s brought plummeting enrollment, dwindling appropriations from the city, leadership changes and an $18.2 million deficit.

That, in turn, led to the firing of 30 percent of the faculty and 40 percent of the school's administrative staff in 1996. Then, federal courts ruled that the school had implemented the reduction in force illegally, forcing UDC to cut more than 20 faculty members this summer to make room for some who had been wrongly let go.

UDC officials closed the deficit and have said in recent months that they are concentrating on building enrollment and making the curriculum more relevant to today's job market.

But early this month, Nimmons and other school and city officials were sued by a former UDC acting chief financial officer, Sherrilyn Silver. In a $10 million lawsuit filed in federal district court, Silver alleges that her job at UDC had been terminated in 1998 after she had exposed criminal activities, gross mismanagement and corruption in UDC's operations.

Nimmons said he believes that false allegations are being made about him and UDC by disgruntled employees, some of whom were being forced to leave the university as part of the effort to reinstate those wrongly fired three years ago.

"This is the beginning. It's going to get uglier," Nimmons said. "I'm telling you one thing. I'm here to stay and I'm going to do my job. The wannabes need to take note: I'm here to stay."