The redacted document reveals that on July 11, 1956, the agency got a tip that an anonymous male caller phoned the Daily News to report that the actress's company, Marilyn Monroe Productions, was 'filled with communists' and that money from the company was being used to finance communist activities.
The file continues up until the months before her death, and also includes several news stories and references to Norman Mailer's biography of the actress, which focused on questions about whether Monroe was killed by the government.
There have been two major government investigations into Monroe's demise - the original inquiry immediately after her death and another effort by the Los Angeles District Attorney's Office in 1982.
The second inquiry, released in December 1982, reviewed all files available investigative reports, including files compiled by the FBI on her death. The records, the DA's office noted, were 'heavily censored.'
'On the basis of my own involvement in the case, beginning with the autopsy, I would call Monroe's suicide "very probable,"' Noguchi wrote. 'But I also believe that until the complete FBI files are made public and the notes and interviews of the suicide panel released, controversy will continue to swirl around her death.'