The letter, dated Sept. 21 and published Friday by the Republican chair of the committee, Sen. Chuck Grassley, does not detail why Clinton made the request, except that she did so on Aug. 30. An aide to Clinton did not respond to a request for comment.
At the time, the White House announced that it was also reviewing the security clearances of other former top officials, such as FBI Director James Comey, Director of National Intelligence James Clapper, National Security Advisor Susan Rice, National Security Agency Director Michael Hayden and Deputy Attorney General Sally Yates.
But Clinton was not on the list.
The letter also says five other State Department officials, including Clinton's longtime aide Cheryl Mills, had their security clearances withdrawn, too. The names of the other four individuals are redacted, but all five had been designated as "researchers" by Clinton, allowing them to keep their clearance after they left the department.
Grassley had asked the State Department last year about the status of Clinton's security clearance and that of her top aides.
In 2016, while running for president against Trump, Clinton was investigated by the FBI and the State Department for her use of a private email server while secretary, but she was never charged with any crime, although Comey said he believed she had been "extremely careless."
The department's Bureau of Diplomatic Security will investigate whether any rules or laws were broken by Clinton's staffers after all their emails are reviewed to determine their classification status, according to the letter.
Grassley's office released the letter Friday night despite a warning from the State Department not to do so: "We request that you protect the information in this letter, as it is not public and generally not appropriate for public release... Should you wish to disclose any portions thereof, we ask that you provide the Department with a reasonable opportunity to inform the Committee of any sensitive information that should be safe-guarded," wrote acting Assistant Secretary of State for Legislative Affairs Charles Faulkner.
It's unclear whether Grassley's office did so.
The State Department would only confirm that Clinton made the request, referring further questions to Clinton.
"Back in August, Admiral William McRaven penned a letter in the Washington Post in the aftermath of Trump revoking @JohnBrennan’s security clearance," Merrill tweeted. "In his letter, he admonishes President Trump for this petty act, and says that Trump’s time as President has “embarrassed us in the eyes of our children, humiliated us on the world stage and, worst of all, divided us as a nation. Who is Admiral McRaven? A partisan? No. He headed Joint Special Operations Command during the rescue of Captain Phillips. He was the architect of the raid that killed Osama Bin Laden. A prominent Republican once said that he had “literally written the book on Special Operations.
"Admiral McRaven has served both Republican and Democratic Presidents, and is a man of honor whose service to this country and heroism is virtually unrivaled," he continued. "Secretary Clinton has great respect for Admiral McRaven. She read this message & decided to take the step of voluntarily withdrawing her security clearance, which she maintained after leaving her post as Secretary of State to write her book, customary for former Secretaries."