Story highlights Bryan Pagliano, a former Hillary Clinton staffer who help set up her private email server, has accepted an immunity offer from the FBI and the Justice Department to provide an interview to investigators

The FBI has been asking for Pagliano's cooperation for months

Washington (CNN) Bryan Pagliano, a former Hillary Clinton staffer who helped set up her private email server, has accepted an immunity offer from the FBI and the Justice Department to provide an interview to investigators, a U.S. law enforcement official told CNN Wednesday.

The FBI has been asking for Pagliano's cooperation for months as dozens of investigators pored over thousands of Clinton emails in a secure room on the fourth floor of FBI headquarters.

The probe shifted into a new phase recently as investigators completed the review of the emails, working with intelligence agencies and the State Department to determine whether they were classified.

The Washington Post first reported Pagliano's cooperation.

"As we have said since last summer, Secretary Clinton has been cooperating with the Justice Department's security inquiry, including offering in August to meet with them to assist their efforts if needed," said Brian Fallon, a spokesman for Clinton's presidential campaign.

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