A hard drive containing personal information of White House staff and visitors during former U.S. President Bill Clinton's administration is missing from the U.S. National Archives and Records Administration, the agency said.
The hard drive, containing an "as yet unknown" amount of personal data, was discovered missing in April, the National Archives said in a statement. The hard drive contained copies of electronic storage tapes from the Executive Office of the President, the agency said.
The agency "takes very seriously the loss of an external hard drive" containing personal information, said the statement, released Tuesday.
National Archives staff has reported the missing hard drive to senior officials there, including the agency's inspector general.
The agency also informed the U.S. Computer Emergency Readiness Team at the Department of Homeland Security, congressional staff and a Clinton representative, the agency said.
The agency is preparing to notify people whose personal information was included on the hard drive, the National Archives said. In addition, the agency's Office of Inspector General has begun a criminal investigation.
The National Archives "immediately undertook a review of our internal controls" and has improved security processes, said the agency, which serves as the record keeper for the U.S. government.
Representative Edolphus Towns, a New York Democrat and chairman of the House Committee on Oversight and Government Reform, said the National Archives inspector general's office briefed committee staff Tuesday about its investigation into the data breach.
The U.S. Federal Bureau of Investigation is also conducting a criminal investigation, Towns said in a statement.
"I am deeply concerned about this serious security breach at the National Archives," Towns said.
Committee members will get briefings into the ongoing investigations so they "can begin to understand the magnitude of the security breach and all of the steps being taken to recover the lost information," he added.