A top aide to Hillary Clinton is under scrutiny from the State Department's inspector general over her overlapping work for the government and for the Clinton Foundation.

The controversial charity was hit with a subpoena last fall for documents related to projects that required the State Department's approval as well as records related to top Clinton aide Huma Abedin, according to a report Thursday by the Washington Post.

Abedin's tenure has come under scrutiny by the State Department watchdog and congressional panels in the past because her simultaneous employment at the Clinton Foundation and by the federal government could have led to potential conflicts of interest.

Last spring, the Clinton Foundation's activism with donors who had interests on Clinton's desk stirred speculation that the former secretary of state may have used her position to favor her charity's most generous contributors.

The State Department inspector general probe is entirely separate from an FBI investigation into Clinton's use of a private server to shield her official communications.

An inspector general cannot charge anyone with a crime.

But the independent government watchdogs can make referrals to the Justice Department and recommendations to the agencies they oversee.

A referral from the inspectors general for the State Department and the intelligence community sparked the FBI probe of Clinton's server use, for example.

The Post report noted the "full scope" of the inspector general inquiry into the Clinton Foundation and Abedin's role there was "unclear."

Abedin is presently vice chair of Clinton's presidential campaign.