Also collected data from social networks including Twitter, Facebook

Under the intense scrutiny of lawmakers following the recent exposes on its covert surveillance, the National Security Agency boss General Keith Alexander conceded that the Agency recently ran a programme that entailed the collection of Americans’ mobile phone location data.

Facing sharp questions at a Senate Judiciary Committee hearing on Wednesday, Gen. Alexander admitted that during 2010-11 the NSA scooped up location data on U.S. citizens for a secret pilot project following a report in the New York Times that this programme yielded “samples in order to test the ability of its systems to handle the data format.”

The latest revelations come on top of prior acknowledgement by the NSA and Director of National Intelligence James Clapper that telephone “meta-data” or call “envelope” information has been secretly reviewed by U.S. intelligence for years.

Since Edward Snowden, former NSA contractor-turned-whistleblower, supplied the Guardian newspaper and other media with classified documents outlining specifics of NSA surveillance the U.S. Congress has held numerous hearings where lawmakers have sought further information on the operations and whether they were consistent with the laws within the Foreign Intelligence Surveillance Act.

Earlier this week Gen. Keith Alexander also testified to the Senate Judiciary Committee that the NSA collected data from social networks including Twitter, Facebook and other private databases “to hunt terror suspects.”

He indicated that although not all social network searches were authorised by the FISA Court, the agency's actions are “proper and audited internally,” and were not used to build dossiers or personal files on Americans. Gen. Alexander said the New York Times report on these searches were “inaccurate and wrong.”

Regarding the surveillance on mobile phone location data, Gen. Alexander answered questions about whether it would form part of any “dragnet” operations by the Agency responding, “This may be something that is a future requirement for the country, but it is not right now, because when we identify a number, we can give that to the Federal Bureau of Investigation.”

He added that when the FBI then get their probable cause to justify obtaining the data, “They can get the location data that they need.”

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