Paula Broadwell, the woman reported to be having an affair with CIA Director David Petraeus, sent harassing emails to State Department official, the AP reported.
Jill Kelley, the woman who received emails from Broadwell that prompted her to alert FBI, reportedly works as a State Department military liaison.
According to the Washington Post, the woman was "frightened" for her safety and contacted the FBI for protection. The Post describes the emails as "threatening."
The New York Times reported that the woman's complaint led the FBI to learn of Petraeus' affair. According to the Times, officials decided to investigate Broadwell and stumbled upon emails that revealed the relationship.
The official says 37-year-old Jill Kelley in Tampa, Fla., received the emails from Petraeus biographer Paula Broadwell that triggered an FBI investigation.
The official was not authorized to discuss the case publicly and spoke on the condition of anonymity.
Another person who knows Kelley and Petraeus confirmed their friendship and said she saw him often.