Story highlights The scope of the FBI inquiry or when it began was not immediately clear

The FBI will at times begin an inquiry as a preliminary step before deciding whether an investigation is warranted

Washington (CNN) The FBI recently opened an inquiry into Missouri Gov. Eric Greitens, two US officials told CNN, as he fights an allegation of blackmail and faces calls to resign just a year into his job.

While the FBI has not commented on the existence of any inquiry or formal investigation into Greitens, the St. Louis circuit attorney's office announced last week that it is investigating Greitens' conduct following an explosive story that forced the Republican governor to acknowledge having had an extramarital affair and confront an allegation of blackmail.

James Bennett, Greitens' lawyer, told CNN on Friday that the governor "has not been contacted at any time by the FBI, and we are not aware of any interest by the FBI in this personal matter that took place years ago." Bennett added that they are also not aware of any interest by the FBI in matters unrelated to the affair.

"It is the long-standing policy of the US Department of Justice that the FBI does not confirm or deny the existence of an investigation," an FBI spokeswoman told CNN.

The scope of the FBI inquiry or when it began was not immediately clear. The FBI will at times begin an inquiry as a preliminary step before deciding whether an investigation is warranted.