The State Department released more than 7,000 pages of e-mails sent or received by Hillary Clinton as part of an ongoing probe into her private e-mail server. The Post’s Anne Gearan discusses their content and what these releases mean to Clinton’s 2016 presidential campaign. (Julie Percha/The Washington Post)

While she was secretary of state, Hillary Rodham Clinton wrote and sent at least six e-mails using her private server that contained what government officials now say is classified information, according to thousands of e-mails released by the State Department.

Although government officials deemed the e-mails classified after Clinton left office, they could complicate her efforts to move beyond the political fallout from the controversy. They suggest that her role in distributing sensitive material via her private e-mail system went beyond receiving notes written by others, and appears to contradict earlier public statements in which she denied sending or receiving e-mails containing classified information.

The classified e-mails, contained in thousands of pages of electronic correspondence that the State Department has released, stood out because of the heavy markings blocking out sentences and, in some cases, entire messages.

The State Department officials who redacted the material cited national security as the reason for blocking it from public view.

Clinton, who is seeking the Democratic presidential nomination, was one of about four dozen State Department officials whose e-mails were redacted because of national security concerns, according to a Washington Post review. Those officials included top aides such as Jake Sullivan and Cheryl Mills, some of whom would be likely to fill out senior roles in a Clinton administration. All told, 188 of the e-mails the State Department has released contain classified material.

Catch up on the controversy and read the emails

The extent of the redactions in e-mails sent by Clinton and others, including ambassadors and career Foreign Service officers, points to a broader pattern that has alarmed intelligence officials in which sensitive information has been circulated on non-secure systems. Another worry is that Clinton aides further spread sensitive information by forwarding government e-mails to Clinton’s private account.

But it also highlights concerns raised by Clinton and her supporters that identifying classified material can be a confusing process, and well-meaning public officials reviewing the same material could come to different conclusions as to its classification level.

Clinton’s use of a private e-mail server has become an issue for her campaign.

The intelligence community’s inspector general had previously identified four e-mails out of a sample of 40 that had been sent on her server and contained classified information, including two that involved top-secret information. In those cases, however, people who have reviewed the e-mails said that Clinton did not write them.

The FBI is investigating whether Clinton’s e-mail setup may have compromised national security information. Officials have said that Clinton is not a target of the inquiry.

Nick Merrill, a Clinton campaign spokesman, said the heavy redactions in some of Clinton’s e-mails had been expected.

“This has been the case in previous releases and may well be the case in subsequent ones,” he said. “It is not surprising given the sheer volume of intelligence community lawyers now involved in the review of these e-mails.”

Merrill pointed to “competing assessments among the various agencies about what should and shouldn’t be redacted.”

State Department spokesman John Kirby said that “classification is not always a black-and-white, binary judgment. Responsible people can draw different conclusions.”

But the presence of classified information in e-mails Clinton wrote appears to contradict her assurances that she sent no such material.

“I have said repeatedly that I did not send nor receive classified material, and I’m very confident that when this entire process plays out that will be understood by the everyone,” she said last week during a Democratic Party meeting in Minneapolis. She said that government officials may now be making different determinations after the fact, but “it does not change the fact that I did not send, nor receive, material marked classified.”

In December 2014, Clinton turned over to the State Department more than 30,000 e-mails she had sent and received during her tenure as secretary. The agency is reviewing and preparing them for public release. A judge has ordered the department to release the e-mails on a rolling basis, completing the process by January. The State Department said Monday that it has released about 25 percent of the archive.

The sensitivity of the redacted information in Clinton’s e-mails is not publicly known. Government officials who have seen some of the correspondence say the conversations are generally benign. Some discuss classified programs or topics that have become well-known through public reporting, said the officials, who spoke on the condition of anonymity to describe classified information.

One e-mail Clinton wrote in October 2009 was addressed to former senator George J. Mitchell (D-Maine), who was a special envoy for peace in the Middle East. The entire message, as released by the State Department, is blacked out and tagged with a designation noting that the information was classified. The only part now public is Clinton’s opening: “George . . . .”

Another note went from Clinton to Melanne Verveer, who was ambassador for global women’s issues, on Dec. 9, 2010. It was entirely withheld from release. The subject line reads, “Re: latest . . .,” with the rest redacted, making it impossible to discern the topic of the exchange.

Like other e-mails, it was withheld based on State Department reviewers’ conclusion that it contained “foreign government information” and “foreign relations or foreign activities of the United States, including confidential sources.”

The e-mails offer hints that Clinton aides were attuned to the need to handle some information with care in more secure settings.

Sullivan e-mailed Clinton a day before Christmas Eve in 2010, for instance, referring to “some interesting reports from the Pal side” that had been passed along from a State Department diplomat, presumably referring to Palestinians. Sullivan suggested a discussion “if you have a moment to talk secure.”

Some of the classified e-mails were written by top aides, as well.

Sullivan in a December 2010 note described for Clinton the results of two phone calls — one in which Vitaly Churkin, Russia’s representative to the United Nations, called a top State Department official. The details provided by Sullivan, a campaign adviser widely considered a potential national security adviser if Clinton is elected, were withheld from public view.

In several exchanges, Verveer forwarded Clinton accounts of confidential reports from Foreign Service officers giving updates from their posts. She shared long notes from the U.S. ambassador to Bangladesh describing what he learned in a private dinner with senior officials in that country amid a major embezzlement scandal. Most of those messages were redacted.

“Maybe more than you want to know,” Verveer writes Clinton in one note titled, “Re: dinner with Gowher.” The reference is to Gowher Rizvi, international affairs adviser to Bangladesh’s prime minister.

Verveer, now the director of a women’s institute at Georgetown University, did not respond to messages seeking comment.

Alice Crites contributed to this report.