Hillary Clinton (left) and aide Huma Abedin greet attendees after a Democratic presidential debate, Nov. 14, 2015, in Des Moines, Iowa. Mandel Ngan/AFP/Getty Images

U.S. State Department investigators last year issued a subpoena to the Bill, Hillary and Chelsea Clinton Foundation seeking documents about projects run by the charity that may have required U.S. government approval when Hillary Clinton was secretary of state, the Washington Post reported on Thursday.

A U.S. official said the matter was being investigated by the Inspector General, the State Department's internal watchdog.

Citing unnamed sources for the report, the Post said the subpoena issued in the fall also asked for records related to senior Clinton aide Huma Abedin, who for six months in 2012 simultaneously worked for several employers including the State Department, the foundation, and Clinton's personal office.

The report follows a Reuters investigation last year that found the Clinton Foundation's flagship health project did not submit new or increased payments from at least seven foreign governments to the State Department for review, in breach of the ethics agreement Clinton signed with the incoming Obama administration in order to become secretary of state.

Clinton, who is running for the Democratic nomination in the Nov. 8 presidential election, has been criticized for using a private email account hosted on a private computer while secretary of state from 2009 to 2013, a matter the FBI is investigating.

Spokesmen for Clinton's campaign and the Clinton Foundation and a lawyer for Abedin did not immediately respond to Reuters requests for comment. A spokesman for the Inspector General also declined to comment.

The Post quoted an unnamed foundation representative as saying the initial document request had been narrowed by investigators and that the foundation was not the focus of the probe. It said there was no indication that the investigators were looking at Clinton.

"The full scope and status of the inquiry, conducted by the State Department’s inspector general, were not clear from the material correspondence reviewed by the Washington Post," the paper said.

Sources familiar with investigations into the controversy surrounding Clinton's private email server said they had no reason to believe any government agency was conducting any kind of inquiry into possible criminal violations related to the former secretary of state.

(Reporting by Mark Hosenball; Writing by Mohammad Zargham; Editing by Andrew Hay)