Federal agents were investigating the late San Francisco Supervisor Harvey Milk and the late mayor of San Francisco George Moscone for alleged political corruption when both men were murdered in November 1978, according to Federal Bureau of Investigation files.

The man convicted of killing both men, then-Supervisor Dan White, was also the subject of a separate FBI political corruption probe before he gunned down Moscone and Milk at San Francisco's City Hall.

Agents in the FBI's San Francisco bureau were looking into whether Moscone and Milk had collaborated to "defraud the federally sponsored San Francisco Community Development Fund," according to documents obtained by San Francisco blogger and gay rights activist Michael Petrelis. (The relevant pages from those documents can be seen here.)

FBI officials were also investigating whether Moscone had received $10,000 "for favorable treatment in the building of a controversial McDonald's restaurant," according to the files.

White was being investigated for allegedly securing favorable treatment for an unnamed party in exchange for a deal involving San Francisco's Pier 39, a popular tourist venue where White leased space to operate a fast-food restaurant.

The memo obtained by Petrelis that discusses the investigations is stamped November 30, 1978, three days after White shot the two men. It notes that the "investigations should not be discussed outside the bureau."

Danny Nicoletta, who worked with Milk in a San Francisco camera store frequently shown in the 2008 movie Milk, said he wasn't surprised to hear the FBI had been investigating all three men.

"In terms of what the political climate was at that time, one would assume the FBI had looked into all of those gentleman," Nicoletta said, adding that Milk, the first openly gay elected official, was "basically a political maverick" who held office in a place and time when people were "antagonistic towards the government."

Tim Wilson, a librarian with the Gay and Lesbian Center at the San Francisco Public Library, noted there was division within the gay rights movement as well in the 1970s.

"Harvey was more grassroots, whereas others who were prominent, politically active gay men were part of the 'machine,'" Wilson said. "Their ways of getting political backing were more similar to the political establishment. Harvey, from what I understand, was more coming from the hippie side -- not necessarily establishment, trying to give a voice to unvoiced folks. Within the gay movement there were different camps about how decisions should be made and who should get the nod for political endorsements."

Nicoletta added that he thought the White House "would have been highly curious about what was going on with LGBT issues in San Francisco at that time."

"I also think they would have been very happy to find something to destabilize [Milk]," Nicoletta continued, "but as I remember it he was pretty squeaky clean."

Special Agent Joseph Schadler, who works in the FBI's San Francisco bureau, said public corruption probes are one of the agency's "highest priorities," but cautioned that an investigation does not mean a crime was committed.

"At any point in time, in any major city, we have public corruption investigations," Schadler said. "Whether there's anything there is another matter."

Patti Hansen, a public affairs specialist with the FBI's San Francisco Bureau, said she could not speak to the outcome of the more than 30-year-old investigations, but said the FBI does not usually pursue investigations after the main subjects of probes have died.

"If they're dead, then there's nobody for us to prosecute," Hansen said.

Blogger Petrelis is still seeking additional files from the FBI about the probes. The files he has now, however, contain a document signed by Milk suggesting he lived on Henry Street around the time he was murdered, not above the camera store on Castro Street as the movie indicates.

The files also contain a statement (which can be seen here) made in 1983 by an unidentified person who said he had contacted White after reading a comment he made in newspaper articles in early 1978 and was invited by White to visit him in City Hall.

The person says he told White he wanted to pursue the possibility of recalling Moscone from office and White said not to worry because by the end of the year he would "get rid of three bastards," mentioning Milk, Moscone and a third person whose name was redacted in the document.

Roughly eight months later and several days before the murders, the witness reports having heard that "Dan White had gone mad."

"I couldn't sleep that Sunday night, November 26," he said, adding that he approached police officers at City Hall to tell them to "watch for Dan White and search him very carefully."

"All laughed at my statement, saying, 'Dan was a good cop and he's not going to hurt anyone,'" the witness said. The person left the building after stopping by the mayor's office and seeing "enough people there" that he or she believed the mayor would be safe.

Shortly after leaving the building, the witness, who claimed to be friends with the San Francisco Fire Chief and Assistant District Attorney, said they saw emergency vehicles racing to City Hall and learned of the shootings.

The FBI documents indicate the witness also claimed to be friends with the mayor of Jersey City, the U.S. Attorney for Northern California and others. The agents interviewing the person concluded he would not be a good witness in any court cases.

Michael Petrelis contributed research to this report.