This post was updated at 4:45 p.m. ET
Controversy grew on Friday over emails from Hillary Clinton's private server she used while at the State Department, with the agency announcing several documents would be withheld because they had been deemed top secret.
"We can confirm that later today, as part of our monthly FOIA productions of former Secretary Clinton's emails, the State Department will be denying in full seven email chains, found in 22 documents representing 37 pages. The documents are being upgraded at the request of the intelligence community because they contain a category of top secret information," State Department spokesman John Kirby said. "These documents were not marked classified at the time they were sent."
Kirby reiterated that he would not comment on the content or subject of the blocked documents.
The new revelations come at a particularly politically damaging time — just days before the Iowa caucuses on Monday, where the former secretary of state is neck and neck with Vermont Sen. Bernie Sanders.
Clinton's campaign responded that the new roadblock "appears to be overclassification run amok" and that it will "pursue all appropriate avenues to see that her emails are released in a manner consistent with her call last year."
"After a process that has been dominated by bureaucratic infighting that has too often played out in public view, the loudest and leakiest participants in this interagency dispute have now prevailed in blocking any release of these emails. This flies in the face of the fact that these emails were unmarked at the time they were sent, and have been called 'innocuous' by certain intelligence officials," Clinton spokesman Brian Fallon said. "We understand that these emails were likely originated on the State Department's unclassified system before they were ever shared with Secretary Clinton, and they have remained on the department's unclassified system for years. And, in at least one case, the emails appear to involve information from a published news article."
Clinton told NPR's Ari Shapiro last week that was the case in at least one instance, following an initial report that some of the emails had been marked top secret.
"As the State Department has confirmed, I never sent or received any material marked classified, and that hasn't changed in all of these months," Clinton maintained. "This seems to me to be, you know, another effort to inject this into the campaign. It's another leak."
An additional 18 emails, including eight distinct email chains, between Clinton and President Obama will also be withheld under executive privilege. They are not classified, Kirby said, and will eventually be released under the Presidential Records Act.
The announcement of the top secret emails comes as the agency is already behind on its monthly production of emails. The State Department has already made public 43,000 pages of Hillary Clinton's emails, and 1,000 more pages are supposed to come out Friday evening. In a late-night court filing this week, authorities said about 7,000 more pages are not yet ready for release.
"State has moved diligently to process the documents and send them to the appropriate agencies for review, a process that was interrupted by the blizzard that struck Washington, D.C.," the court filing said.
That means at least one more Clinton email dump is coming, after primary voting is underway in several states.
And Clinton also fighting multiple investigations into her decision to use a private email server as secretary of state.
The FBI investigation into Clinton's email has been underway for months now. And while the Justice Department and FBI have been keeping a close hold on information, the probe appears to involve whether any government secrets were compromised and how that came to happen.
The inquiry involves not just Clinton, but some of her close aides who sent her messages. Clinton recently told reporters that she has not been interviewed by federal agents, but that is something that typically occurs near the end of an investigation.
Republicans quickly seized on the revelation of the new top secret emails, saying they "once again raise serious legal questions given the fact Hillary Clinton signed a legally binding agreement obligating her to protect classified material regardless of whether it was marked."
"With even more emails on her secret server found to contain 'Top Secret' information, Hillary Clinton has removed all doubt she cannot be trusted with the presidency," Republican National Committee Chairman Reince Priebus said in a statement. "Hillary Clinton's attempt to skirt government transparency laws by relying exclusively on an unsecure email server in her basement put our national security and diplomatic efforts at risk. And rather tell the American people the truth, Hillary Clinton, her campaign, and her friends in the Obama Administration have obfuscated and misled at every available opportunity. If this isn't disqualifying I don't know what is."
Earlier this week, Clinton told the Quad City Times that her use of a private email server had become a distraction.
"It was a mistake because who wants to put people through all of this?" Clinton said. "I don't want to go through it; I don't want to put a lot of my friends through it. So it was a mistake."
Clinton has said she never sent or received any messages marked classified.
That FBI investigation is far from the only scrutiny the Clinton emails are getting. Reporters and conservative public interest groups have filed federal lawsuits to get copies of those messages.
And Republicans are taking notice. Former Attorney General Michael Mukasey — who served in the George W. Bush administration — published an op-ed accusing Clinton of mishandling classified information, a violation of the law.
Presidential candidate and Florida Sen. Marco Rubio brought up the issue Thursday at the Fox News Channel debate.
"Hillary Clinton is disqualified from being the commander in chief of the United States," Rubio said. "In fact one of her first acts as president may well be to pardon herself. That's because Hillary Clinton stored classified information on her private server."
The email issue is on the agenda in Congress as well. Iowa Republican Sen. Charles Grassley, who leads the Judiciary Committee, has sent two binders full of letters to Clinton, the State Department and the Justice Department.
He wants to know what the FBI is doing, whether it is going to grant immunity from prosecution to the information technology aide who helped set up Clinton's private server, and whether federal agents are investigating dealings between the State Department and donors to the Clinton foundation.
RENEE MONTAGNE, HOST:
And Democratic presidential candidate Hillary Clinton is in Iowa today. No surprise she's trying to fend off rival Bernie Sanders before next week's caucuses. But Clinton is fighting something else as well - multiple investigations into her decision to use a private email server as secretary of state. With us now is NPR justice correspondent, Carrie Johnson. Good morning.
CARRIE JOHNSON, BYLINE: Good morning, Renee.
MONTAGNE: Now, the FBI investigation into Clinton's email has been underway for months. Is there any news on that one?
JOHNSON: Well, Renee, the Justice Department and the FBI have been keeping a close hold on any information about the investigation for clear reasons. It's really politically sensitive. But it appears to involve whether any secrets were compromised and how that came to happen. The inquiry involves, Renee, not just Hillary Clinton but some of her close aides who sent her messages. And Clinton has said she's not been interviewed by the FBI, but that's something we'd expect to happen much later near the end of an investigation. Here's what Clinton said this week to the Quad-City Times about her use of a private email server.
(SOUNDBITE OF ARCHIVED RECORDING)
HILLARY CLINTON: It was a mistake. So who wants to put people through all of this? I don't want to go through it. I don't want to put, you know, a lot of my friends through it. So...
UNIDENTIFIED MAN: Yeah.
CLINTON: ...It was a mistake.
JOHNSON: So to be clear, Renee, Clinton says she never sent or received anything marked classified, in other words, no intent to do anything wrong.
MONTAGNE: And, Carrie, that FBI investigation is far from the only scrutiny those Clinton emails are getting. Who else is taking a look at all of this?
JOHNSON: Well, for starters reporters - a lot of reporters and a lot of conservative groups. There are dozens of ongoing federal lawsuits to get copies of those email messages. The State Department's already made public tens of thousands of pages, and more of those emails are supposed to come out later today, Friday. But they won't be the last batch. I'm hearing we expect - we should expect at least one more email dump next month. And that's after primary voting is underway in several states.
MONTAGNE: And, you know, though, voters don't seem too interested in these emails. It's pretty much the political arena that's focused on the issue. How is it playing out in the political area these days?
JOHNSON: It's been a significant element on the campaign trail. Just in the last week or so, George W. Bush's attorney general, Michael Mukasey, published an op-ed that accuses Clinton of mishandling classified information, which is a violation of the law. And, Renee, it came up last night in the GOP debate on Fox News Channel with Senator Marco Rubio. Here he is.
(SOUNDBITE OF ARCHIVED RECORDING)
MARCO RUBIO: Hillary Clinton is disqualified from being the commander in chief of the United States. In fact one of her first acts as president may very well be to pardon herself...
RUBIO: ...Because Hillary Clinton - Hillary Clinton stored classified information on her private server.
MONTAGNE: Well, amusing but again Clinton denies that. What are Republicans in Congress saying about all this?
JOHNSON: Renee, Congress is not going to be in session very much this year between elections and their vacation schedules. But oversight of Hillary Clinton is going to be a key part of the Republican agenda on Capitol Hill. For instance, Senator Charles Grassley, who leads the Judiciary Committee, has sent a lot of letters to Clinton, the State Department, the Justice Department demanding information. He wants to know what the FBI is doing and whether federal agents are investigating any possible dealings between the State Department and donors to the Clinton Foundation, too.
MONTAGNE: Carrie, thanks very much.
JOHNSON: You're welcome.
MONTAGNE: That's NPR justice correspondent Carrie Johnson. Transcript provided by NPR, Copyright NPR.