Clinton quizzed over emails in 2012
Hillary Clinton was asked by congressional investigators more than two years ago whether she had used a private email account while serving as secretary of state.
The State Department later declined to address the question.
Republican Darrell Issa of California, then the Republican chairman of the House Oversight and Government Reform Committee, asked the State Department about it in a December 2012 letter about officials' use of personal email.
The letter asked if any senior agency officials used personal email to conduct official business.
The State Department responded in March 2013 with details on its email policies but did not address the substance of the request.
The letters were first reported by The New York Times.