The Federal Bureau of Investigation is looking into the security of the private email server that Hillary Clinton used during her tenure as the secretary of state, the Washington Post reported Tuesday, citing unnamed government officials. The investigation comes just days after the latest batch of Clinton’s emails was released by the State Department.

According to the report, FBI officials have so far contacted Platte River Networks -- the Denver-based technology firm that helped manage the private server -- and Clinton’s lawyer David Kendall.

Kendall told the Post that the FBI had contacted him to assess the security of a thumb drive in his possession that contains copies of the emails.

“The government is seeking assurance about the storage of those materials. We are actively cooperating,” he reportedly said.

The responsibility to set up and maintain Clinton’s private server was initially handled by a staffer who was on the payroll of her political action committee before being handed over to Platte River, the Post reported.

The interest in the contents of Clinton’s emails stems from the fact that her use of a private account between 2009 and 2013 violated White House and State Department guidelines. The State Department had earlier proposed to release her emails in January 2016, but the proposal was later rejected by a federal judge who called for them to be made public on a “rolling” basis.

The release of her emails began on June 30, when 3,000 pages -- portions of which were redacted because they were later upgraded to “classified status” -- were made public. The latest batch of her emails was released last week.

The FBI inquiry comes on the heels of a “security referral” received by the Justice Department, alerting it of potentially classified information in Clinton’s emails that was not in the government’s possession. The referral did not accuse Clinton of any wrongdoing and did not seek a criminal probe against her.

“The main purpose of the referral was to notify security officials that classified information may exist on at least one private server and thumb drive that are not in the government’s possession,” Charles McCullough, the inspector general who oversees U.S. intelligence agencies, said in a statement last month, which was also signed by the State Department’s Inspector General Steve Linick.