WASHINGTON (AP) — Top U.S. intelligence officials are revealing more about their spying in an effort to defend the National Security Agency from charges that it has invaded the privacy of Americans on a mass scale.

Yet the latest disclosure — that the NSA tried to track Americans' cellphone locations — is only adding to the concerns of lawmakers.

NSA chief Gen. Keith Alexander told Congress on Wednesday that his spy agency ran tests in 2010 and 2011 to see if it was technically possible to gather U.S. cell-site data. That can show where a cellphone user has traveled. Alexander says the information was never used and the testing was reported to congressional intelligence committees.

Alexander also denied reports that the NSA has mined Americans' social media.

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