Image copyright AP Image caption John Brennan has been CIA director since 2013

US authorities are investigating reports that CIA Director John Brennan's personal email account has been hacked by a high-school student.

The alleged hacker told the New York Post that he had found work-related files such as Mr Brennan's application for a top security clearance.

The CIA said investigations were under way, but did not confirm whether the hack happened.

The teenager making the claim has remained anonymous.

He was described by the New York Post newspaper as "a stoner high-school student" who was angry about US foreign policy.

His Twitter account included links to files which he said were Mr Brennan's contact list, a list of phone calls by a former CIA deputy director and other documents.

There was also a tweet with a list of names - including one claiming to be John Brennan - alongside telephone numbers, email addresses and social-security numbers.

A statement from the CIA said: "We are aware of the reports that have surfaced on social media and have referred the matter to the appropriate authorities."

The alleged hacker also claimed to have breached an email account belonging to Homeland Security Secretary Jeh Johnson.

The use of private email by senior US officials has become a major issue in recent months, since it emerged that White House hopeful Hillary Clinton had done so while secretary of state.