Intelligence Community officials have started working with the State Department team assigned to review all 55,000 pages of former Secretary of State Hillary Clinton's emails in an effort to identify any information in the communications that they believe is classified and should be withheld from disclosure.

In a five-page declaration filed Friday evening in US District Court in Washington, DC, John Hackett, the State Department's top Freedom of Information Act (FOIA) official, said the department last month added Intelligence Community reviewers from five of the 17 intelligence agencies to the project after concerns were raised that Clinton's emails were not being properly vetted for intelligence information.

Hackett's declaration was filed in response to VICE News's FOIA lawsuit against the State Department, filed last January in which we sought all of Clinton's emails. In May, a federal judge ordered the State Department to release a batch of Clinton's emails every month. Hackett said in a declaration that month there was a five-step review process in place for screening Clinton's emails. Now there's a sixth a step, he said.

"The Department recently added another step in the review process, at the recommendation of the Inspectors General for the Department and the Intelligence Community (IC)," Hackett wrote. "These Inspectors General raised concerns about the Department's evaluation of other agencies' equities and recommended that the Department's FOIA Office seek staff support from IC FOIA offices to assist in identifying IC equities. In response to this recommendation, the Department made arrangements for the IC to provide reviewers to assist the Department in identifying potential IC equities in its review of the emails."

The New York Times first revealed in March that Clinton had exclusively used a private email account to conduct official government business during the four years she served as Secretary of State. Open government experts suggested that Clinton's decision to use her personal email was an attempt to thwart FOIA requests. Clinton's work-related emails are considered government records and are supposed to be preserved on the State Department's servers in accordance with the Federal Records Act so that journalists, historians, and the public can access them. The controversy has already taken a toll on Clinton's presidential campaign, according to opinion polls.

Clinton said that she had decided to use a private email account to conduct official business because it was "convenient." She has also repeatedly denied that she sent or received classified information over her email account, which was connected to a private server operated out of her home in New York.

But the New York Times reported last month that a sample review of Clinton's emails by Inspectors General for the Intelligence Community and State Department revealed that there are potentially hundreds that contain classified information. State Department FOIA officials have retroactively classified portions of more than three dozen of Clinton's emails it has released thus far, claiming the information, if released, could pose a threat to national security. The State Department and Intelligence Community Inspectors General have since referred the matter to the Justice Department to determine if sensitive information in the emails was mishandled, and the FBI is also looking into the issue.

McClatchy Newspapers then reported that the classified emails in question contained information from five US intelligence agencies, identified as the National Security Agency, CIA, Defense Intelligence Agency, Office of Director of National Intelligence and the National Geospatial-Intelligence Agency, which maps and tracks satellite imagery. It's likely those are the five intelligence agencies that have now been tasked to work with the State Department team reviewing Clinton's emails.

Hacket said the five Intelligence Community reviewers, whose agencies he did not identify, started working on the review of the emails on July 15. They "perform preliminary screening of emails to identify their agencies' equities."

Last week, the State Department released the third batch of Clinton's communications, which totaled 1,356 emails. But the release fell short of the 15 percent of the more than 33,000 emails a federal judge ordered the State Department to release every month. State Department spokesman Mark Toner said it was due to the stepped-up security review of Clinton's emails. He said the State Department would make up for the "gap."

Hackett, who said the State Department is behind by 1,721 pages, further explained why the department did not meet its goal.

"The IC reviewers had only eight business days, until July 24, to screen documents for the July 31 release," he said in the declaration. "At least part of that time was occupied by administrative and orientation tasks that naturally arise when a worker from one agency is assigned temporary duty at another."

Hackett said the State Department only released Clinton emails last month "that had been screened by the IC reviewers and identified as not having [intelligence] agency equities."

"This screening process could only be completed for enough documents to allow the Department to post 2,206 additional pages on July 31," he said.

Hackett said the department would make up for the shortfall with additional email releases later this month and in September and will be "back on track" by September 30.

"More specifically, the Department plans to release 6,106 or more pages on August 31, bringing the cumulative progress to at least 23.4% (just shy of the Court's goal of 25% for August 31), and 7,156 on September 30, bringing the cumulative progress to 37% (the goal set by the Court for September 30)," he said.

Hackett also noted that the Intelligence Community reviewers are now "fully integrated into the process, and as they gain familiarity with the documents, I expect the screening of emails for IC equities to proceed more quickly." He said the Intelligence Community reviewers would work additional hours, if necessary, to ensure the release of more emails.