A representative for the Clinton Foundation confirmed that the organization was sent a subpoena by the State Department late last year.
The subpoena was sent to Hillary and Bill Clinton's charitable organization 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" in addition to records on Clinton aide Huma Abedin, said CNN.
In 2012, Abedin was simultaneously employed by the State Department, Clinton's personal office and a private consulting firm associated with the Clintons. Abedin is now a top official with Hillary Clinton's presidential campaign.
Full details on the State Department's inquiry were not disclosed by the Washington Post, who first revealed news of the subpoena. The inquiry was conducted by the Inspector General, whom the Washington Post said was not looking at Clinton herself.
Abedin was audited in 2015 when it was found that she'd been overpaid by almost $100,000 while working for the State Department.