Kevin Johnson

USA TODAY

WASHINGTON — The timeline for completion of the federal investigation into Hillary Clinton's use of a private email server while secretary of State is "not tethered to any external deadline," including the looming Democratic convention, FBI Director James Comey said Wednesday.

"There are no special rules for anybody," Comey told reporters. He declined to comment, however, on the substance of the investigation.

At times, Clinton has referred to the inquiry as a "security review,'' recently telling NBC's Today show that such inquiries are common across the government.

"We're conducting an investigation,'' Comey said. "I'm not familiar with the term security review.''

Last week, a U.S. official said the inquiry into the operation of the private email server maintained by Clinton was nearing completion, as investigators have moved to interview a top aide to the likely Democratic presidential nominee.

Longtime Clinton aide Huma Abedin has been interviewed, said the official who is not authorized to comment publicly.

Abedin interviewed in Clinton email case

It is expected that within weeks investigators would move to interview Clinton about her handling of sensitive government information while she served as the nation’s top diplomat.

The official was not aware of any conclusions that investigators have reached in the ongoing inquiry.

Clinton’s use of a private email server while a member of the Obama administration and the inquiry into the security of classified information has shadowed her campaign throughout the primary season.

In a recent interview with MSNBC, Clinton said she had not yet been contacted by federal authorities to set up an interview.

In recent public statements, Comey has said that the investigation was continuing and that the only emphasis was to conduct a thorough review.