Sen. Chuck Grassley, chairman of the Senate Judiciary Committee, said Friday an email suggesting Hillary Clinton asked an aide to remove classification markings from a sensitive document and send it to her over an unsecured network was "disturbing."

"The State Department's latest Freedom of Information Act release contains a disturbing email that appears to show the former secretary of state instructing a subordinate to remove the headings from a classified document and send it to her in an unsecure manner," Grassley said hours after the agency made the email public in a late-night document dump.

"It raises a host of serious questions and underscores the importance of the various inquiries into the transmittal of classified information through her non-government email server," he added.

Grassley questioned how long the State Department had been aware of the email in question and why the record was not released until January.

The Iowa Republican, whose committee oversees implementation of the Freedom of Information Act, also questioned whether the FBI was looking into whether Clinton's staff followed through on her potentially illegal request.

A State Department spokesman declined to specify whether the agency had referred the matter to the Justice Department for review, but said State's own preliminary review did not uncover evidence that the sensitive document was ever pulled off the secure network.

The email was made public through a FOIA lawsuit that will force the release of all 55,000 pages of Clinton's emails by Jan. 29.