WASHINGTON -- The State Department has released more than 500 more documents from former Secretary of State Hillary Clinton's email account.

The department says portions of 64 of the documents were upgraded to the "confidential" level -- the lowest level of classification -- although none of the information was marked "classified" at the time the emails were sent. None of the 562 documents released Friday was upgraded to "secret" or "top secret."

Friday's email release brings the total number of Clinton documents posted on the department's website to nearly 47,000 pages.

Among the emails was a February 2011 exchange between Clinton and former Secretary of State Madeline Albright in which Albright tells Clinton, "Nothing about this is easy."

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A week later, Clinton begins her response by writing, "You're not kidding that nothing about this is easy!"

The documents also contained several references to Libya and Benghazi.

In one October 2012 exchange with aide Jake Sullivan, Clinton discussed a campaign ad, put out by the conservative American Crossroads, that aired after the September attack on the American compound in Benghazi.

"More of Rovian perfidy," Clinton wrote to Sullivan, dismissing the ad with a reference to Karl Rove, the former George W. Bush adviser who co-founded American Crossroads.

Sullivan responded: "Did you watch? Not about the whodunit issue -- this is about Obama going on the View rather than meeting with world leaders."

"But the subtext is his absence or negligence re terrorism and leadership," Clinton replied. Later, she predicted that it would become a flashpoint of the 2012 election, saying "we'll likely see both attacks in debate, on the stump and in ads."

The 1,116 pages made public Friday bring the total page count of released Clinton emails to 46,946.

The State Department plans to finish making her emails public on Feb. 29, a day before the critical Super Tuesday primaries.

Clinton has struggled to put the email controversy to rest as she seeks the Democratic presidential nomination.

The email release comes a day before Nevada Democrats are scheduled to caucus for their chosen candidate. While Clinton has long been expected to win in the state, the latest polling released just days before the caucuses shows a closer race between Clinton and rival Bernie Sanders.