An email forwarded by Hillary Clinton to a colleague that identified a top CIA informant in Libya could trigger an intelligence investigation and add to concerns that she mishandled classified information, according to intelligence sources.

Clinton received an email in March 2011 from her longtime adviser Sidney Blumenthal that identified a covert Libyan source who was reportedly working with the CIA. Blumenthal said his business partner, the late former CIA agent Tyler Drumheller, had given the information to him.

Clinton forwarded the email over her personal server to a colleague, according to emails published on Thursday by Rep. Trey Gowdy (R., S.C.), chairman of the House select committee on Benghazi.

An intelligence source said that the email could trigger an investigation into whether any of the parties violated the Intelligence Identities Protection Act, calling the apparent disclosure "a couple steps above Valerie Plame."

"Once you compromise the cover, there's a whole section of law called the Intelligence Identities Protection Act," said the source. "It's against federal law to disclose the identities or the real names of anybody who works for the CIA or any other part of the intelligence community."

The Intelligence Identities Protection Act prohibits individuals who have access to the identities of covert agents—including CIA intelligence sources—from intentionally disclosing this information to individuals who are not cleared to receive it.

Blumenthal’s email does not say how Drumheller, who was retired from the CIA at the time, received the information. It is also unclear why Drumheller would pass it along to Blumenthal, who was not in government.

Gowdy, in an email to Rep. Elijah Cummings (D., Md.), wrote that the information allegedly passed between Drumheller, Blumenthal, Clinton and her colleague was "some of the most protected information in our intelligence community" and undermined Clinton’s claim that she never sent classified information over her private server.

A former intelligence official also told Yahoo News that the email would likely trigger a "crime report," in which the CIA reports the issue to the Department of Justice’s intelligence division for further investigation into how the covert source’s name was leaked.

"She is exposing the name of a guy who has a clandestine relationship with the CIA on her private, unprotected server," John Maguire, a former CIA officer, told Yahoo.

The FBI is currently investigating whether classified information was mishandled over Clinton’s private server.