The Washington Post first reported
on the subpoena Thursday, saying it was sent to The Clinton Foundation last fall, and sought "documents about the charity's projects that may have required approval from the federal government during Hillary Clinton's term as secretary of state," as well as records on Clinton aide Huma Abedin. The Post report said there is no indication the Inspector General is looking at Clinton herself.
A foundation representative would not comment on details of the subpoena. The representative did say that the investigation has been narrowed since the initial subpoena and that the Clinton Foundation was not the focus of the Inspect General investigation.
A spokesperson for the Inspector General's office declined to comment.
The nature of the Inspector General's inquiry is unclear, but the revelation is the latest in a series that have brought increased scrutiny to Hillary Clinton's tenure as Secretary of State.
Most notably, the FBI is in the process of investigating the security of a private email server used by Clinton to conduct official business while in office. The State Department is also in the process of reviewing the former secretary's emails for public release, and conducting a separate review into whether any information on the server was classified at the time it was sent.
Abedin, who served as Clinton's Deputy Chief of Staff at the State Department and is now a top official on her presidential campaign, was the focus of an audit by the Inspector General last year, which found she had been overpaid
by nearly $10,000 while at State.
A representative for Abedin did not respond to CNN request for comment.
Abedin's employment at the State Department under a "special government employee" provision, which allowed her to work for the Clinton Foundation and a private firm during the same period, has also been the focus a congressional inquiry led by Senate Judiciary chairman Charles Grassley.
Brian Fallon, a spokesman for Hillary Clinton's campaign, told CNN's Wolf Blitzer the Inspector General's office has been conducting "fishing expeditions."
Fallon said "questions need to be asked about the independence of that office," and called out a couple OIG staffers by name, including a woman who used to work for Grassley.