The federal investigation of Robert L. Green, widely believed to be dormant as of a year ago, suddenly came to life when federal investigators began reconstructing missing city records of spending by Mayor Marion Barry's office, according to sources close to the investigation.

Investigators, who were launched on a seemingly unrelated probe of expenditures from Barry's ceremonial fund and other office accounts, stumbled upon the complex financial transactions that Green allegedly used to conceal his use of government funds for the 1983 purchase of a stereo and large-screen television while serving as president of the University of the District of Columbia.

The city's records of the ceremonial fund and other accounts for that period had been destroyed, according to city officials. But in subpoenaing records from a bank that held the funds, investigators found two checks they later determined had covered the purchase of the items.

Green was indicted Wednesday on charges of stealing the $2,000 television and $1,400 stereo and lying to a federal grand jury about how the items were purchased and what he did with them. Green, now an administrator with a community college in Cleveland, has said he did not take anything that didn't belong to him and does not believe he made any false statements to a grand jury.

The indictment of Green came more than two years after FBI agents, prompted by a letter from UDC Trustee Joseph Webb, began reviewing records of his expenditures as the university president. The initial allegations, which led to Green's resignation in August 1985, focused on numerous university expenditures for flowers, trips and consultants.

University records showed Green billed UDC for such expenses as a trip to a tennis resort in Florida, a health club membership and a trip to the funeral of his wife's grandmother. The records also showed he used the university's tax exemption to avoid paying sales tax on more than $2,200 in personal items that he and his wife bought at area stores.

In an audit, D.C. Auditor Otis H. Troupe found that Green hired five consultants without contracts who apparently produced no work but received $3,619 in fees from the president's representation fund.

Early this year, Green was telling associates that the federal investigation was over and he had been cleared of any wrongdoing. However, the prosecutor in charge of probing Barry's office accounts, Daniel J. Bernstein, was apparently just beginning to focus on Green.

No further charges against Green are expected, according to sources. But investigators are attempting to determine whether others, including Robert Robinson, a former administrative aide to Barry, misused the mayor's office accounts. Robinson, who has denied any wrongdoing, controlled the accounts from 1984 until he resigned last year.

According to sources, UDC officials testified before a grand jury that Green or his wife identified the stereo and a large-screen television set also allegedly purchased with government funds, as their own property in an inventory conducted at the university-owned president's home after Green resigned.

UDC officials said in interviews that they believed the Greens because they did not know that money from the mayor's ceremonial fund and an account called the Mini-Art Gallery Fund had been used to cover the purchase of the items.