A handful of emails forwarded to Hillary Clinton’s personal server while she was secretary of state contained references to undercover CIA officers — including one who was killed by a suicide attack in Afghanistan, according to U.S. officials who have reviewed them.

But contrary to some published reports, three officials said there was no email on Clinton’s server that directly revealed the identity of an undercover intelligence operative. Rather, they said, State Department and other officials attempted to make veiled references to intelligence officers in the emails — references that were deemed classified when the messages were being reviewed years later for public release.

Hillary Clinton takes a question at a rally in New Hampshire on Feb. 3, 2016. ADREES LATIF / Reuters

In one case, an official said, an undercover CIA officer was referred to as a State Department official with the word “State,” in quotes, as if to suggest the emailer knew the officer was not actually a diplomat. In another case, an email refers to “OGA” for “other government agency,” a common reference to the CIA. Yet another now-classified email chain originated with a member of the CIA director’s staff, leading some officials to question how Clinton could be blamed.

Related: Judge Sets Hearing Date in Clinton Email Case

Clinton campaign spokesman Brian Fallon said no intelligence officer had been identified in the emails, and that misleading details from the emails were being leaked to hurt the candidate.

"This shows yet again how the leaking of selective details gives a completely false impression about what is actually contained in the emails forwarded to Hillary Clinton,” said Fallon. “Whenever the full contents of these emails are learned, there is invariably less than meets the eye."

Twenty-two of the emails were fully withheld from public release last week on the grounds that the information in them is “Top Secret,” meaning its disclosure now would cause “exceptionally grave damage to the national security.” But intelligence officials and congressional officials who oversee them are divided over whether that is actually the case.

Nonetheless, the issue promises to dog Clinton’s presidential campaign. Since the messages are classified, people with the clearances to see them are free to characterize them as they wish. Republicans tend to see them as highly problematic for Clinton, while Democrats see the opposite. The FBI is investigating the security of Clinton’s email arrangement, and the FBI would also have jurisdiction to investigate the mishandling of classified information.

Sen. Marco Rubio, the Florida Republican running for president, serves on the Senate Intelligence Committee. “If someone on my staff did what she did…they would be fired and they would be prosecuted,” he said recently.

But Rep. Adam Schiff of California, a Clinton supporter who is the ranking Democrat on the House Intelligence Committee, offered a different view after reading the emails.

“The determination that something is top secret, for many people connotes that these are the most closely held secrets, that their revelation would be extremely damaging,” he said. “There are potentially programs that are talked about all the time in the press that fit within that category.”

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

“Whenever the full contents of these emails are learned, there is invariably less than meets the eye"

Schiff may have been referring to CIA drone strikes, which officials have said are discussed in the now-classified emails. The strikes are highly classified but are also widely discussed over unclassified channels in Washington and elsewhere.

The email message about the dead officer was created by a Defense Department official, Jeremy Bash, who at the time was chief of staff to then-Defense Secretary Leon Panetta. It concerned Dario Lorenzetti, a Fort Worth native — later revealed to be a CIA officer — who died Oct. 13, 2012, when an Afghan intelligence operative detonated a suicide vest in a so-called “Green on Blue” attack. The email was sent on the day of the attack after Lorenzetti’s death was confirmed.

Lorenzetti’s association with the CIA was leaked by anonymous officials to reporters four days after his death and widely reported in the news media, though his CIA cover was not lifted until later. Some of his obituaries listed him as a State Department officer.

“As you’ll be hearing,” the Bash email begins, “an Afghan (intelligence) officer pulled the ripcord on a vest in front of coalition guys loading a helicopter. Total of 14 either killed or wounded — some U.S., some Afghans. Right now we think one U.S. mil killed and one wounded.”

U.S. Democratic presidential candidate Hillary Clinton speaks as her husband former President Bill Clinton and their daughter Chelsea accompany her at a campaign rally in Des Moines, Iowa January 31, 2016. BRIAN SNYDER / Reuters

The next paragraph of the email, which was released Friday and is now posted on the State Department’s website, has been whited out and classified “Secret.” Officials who have reviewed the uncensored version say Bash was attempting to preserve the CIA officer's cover. But some of the language he used, now that Lorenzetti is known to have been a CIA officer, could be read as a U.S. government acknowledgement that CIA officers pose as State Department personnel in a specific country, Afghanistan — something widely known but not formally admitted. Therefore, the section of the email was classified and blocked from public release.

Bash, who was Panetta’s chief of staff while Panetta was CIA director, sent the email to four people — including George Little, a Pentagon spokesman who was a former CIA spokesman, and Philippe Reines, an aide to Secretary of State Clinton.

Bash ends the email by instructing Little, the former CIA spokesman, to “please lash up with (blank)” — presumably either the spy agency or one of its employees.

Reines forwarded the email to Clinton State Dept. aides Cheryl Mills and Jake Sullivan, who forwarded it to Clinton. There is no record of Clinton commenting.

“If someone on my staff did what she did…they would be fired and they would be prosecuted”

Bash, in an interview, said the email was not classified when it was sent or forwarded, and "did not reference the individual's name, employer, nor any identifying description or information."

Once the CIA posthumously lifted Lorenzetti's cover, Bash added, "the original unclassified email could be read to confirm the general use of cover, prompting the redactions we now see. But any suggestion that this email contained confirmation about the person or his cover, or any inappropriate information, is flat wrong."

The 2012 email wasn’t the only one referencing a CIA officer or program, officials said. The references were indirect, and Clinton made no comment about them, the officials said.

Some of the references to covert intelligence officers, and other discussions of CIA drone strikes, were against classification rules and were “sloppy,” one official said. But views are split on whether they were damaging to national security.

It’s unclear, the officials said, whether the emails would have provided significant insights to foreign intelligence agencies, if, as many experts say is possible, Clinton’s private server was penetrated or hacked.

The messages at issue are part of a longstanding pattern of senior officials at the State Department and other government agencies trying to talk around classified information over email, sometimes unsuccessfully.

What makes Clinton’s case different is her use of a home server to transmit emails about government business. The issue has continued to be a factor in her front-running campaign for the Democratic presidential nomination. However, given that the State Department’s email system has been penetrated by hackers linked to Russian intelligence, it’s far from clear whether the material would have been any more secure had Clinton used State’s unclassified email system.

Clinton and her senior aides had access to secure messaging and telephone systems, but they were not as convenient as email.

As the Associated Press has reported, State Department emails previously made public show a history of classified information slipping into unclassified email. Examples have been posted on the State Department’s website in response to Freedom of Information Act requests. Although the classified information has been redacted, it is possible to glean insights into the sensitivity from the context.

In emails about the 2012 attack on a U.S. diplomatic facility in Benghazi, Libya, department officials using state.gov accounts discussed the movement of Libyan militias and the locations of key Americans.

An email from diplomat Alyce Abdalla, sent the night of the attack, appears to report that the CIA annex in Benghazi was under fire. The email has been largely whited out, with the government citing the legal exemption for classified intelligence information. The existence of that facility is now known; it was a closely-held secret at the time.

In five emails from state.gov email accounts that date to Condoleezza Rice’s tenure as secretary of state during the Bush administration and have been publicly released after FOIA requests, large chunks are censored on the grounds that they contain classified national security or foreign government information.

They include a December 2006 email in which diplomat John J. Hillmeyer appears to have pasted the text of a confidential cable from Beijing about China’s dealings with Iran and other sensitive matters.

Large portions of the email were marked classified and censored before release.

Clinton insists she didn’t send or receive information marked classified. But she signed a non-disclosure agreement acknowledging that information can be classified regardless of whether it is “marked or unmarked.”