WASHINGTON — The National Security Agency (NSA) conducted a secret pilot project in 2010 and 2011 to test the collection of bulk data about the location of Americans’ cellphones, but the agency never moved ahead with such a programme, according to intelligence officials.

The existence of the pilot project was reported on Wednesday morning by The New York Times, and later confirmed by Mr James Clapper, the Director of National Intelligence, at a Senate Judiciary Committee hearing. The project used data from cellphone towers to locate people’s cellphones.

In his testimony, Mr Clapper revealed few details about the project. He said the NSA does not currently collect locational information under Section 215 of the Patriot Act, the provision the government says is the legal basis for the NSA’s once-secret programme under which it collects logs of all domestic calls from telephone companies.

“In 2010 and 2011, NSA received samples in order to test the ability of its systems to handle the data format, but that data was not used for any other purpose, and was never available for intelligence analysis purposes,” Mr Clapper said.

He added that the NSA had promised to notify Congress and seek the approval of a secret surveillance court in the future before any locational data was collected using Section 215.

An official familiar with the test project said its purpose was to see how the locational data would flow into the NSA’s systems. While real data was used, it was never drawn upon in any investigation, the official said. It was unclear how many Americans’ locational data was collected as part of the project, whether the agency has held on to that information or why the programme did not go forward.

But Senator Ron Wyden, an Oregon Democrat who receives classified briefings as a member of the Intelligence Committee, and who has raised concerns about cellphone location tracking, said in a statement that there was more to know about the matter than the government had now declassified.

“After years of stonewalling on whether the government has ever tracked or planned to track the location of law-abiding Americans through their cellphones, once again, the intelligence leadership has decided to leave most of the real story secret — even when the truth would not compromise national security,” Mr Wyden said.

General Keith Alexander, the Director of the NSA, who also testified on Wednesday at the hearing, sharply criticised an article on the agency in The New York Times on Sunday. He said it was “flat wrong” that the agency was “creating dossiers on Americans from social networks”. He added that “we’re not creating social networks on our families”.

The article, based on documents leaked by former NSA contractor Edward Snowden, said the agency changed a policy several years ago to allow “contact chaining” of Americans who had been in touch, directly or indirectly, with foreign intelligence suspects, using phone and email logging data.

It also described the process of data “enrichment”, by which other data — including information that is publicly or commercially available — is added to flesh out analysts’ understanding of people associated with various phone numbers in the social network analysis.

The article said it was not known how many Americans’ data was used in this process.

The Chairman of the Senate Judiciary Committee, Senator Patrick Leahy, a Democrat of Vermont, said on Wednesday that he was drafting legislation to eliminate the NSA’s ability to systematically obtain Americans’ calling records.

“The government has not made its case that bulk collection of domestic phone records is an effective counterterrorism tool, especially in light of the intrusion on American privacy,” Mr Leahy said.

But Senator Dianne Feinstein of California, the Chairwoman of the Senate Intelligence Committee, warned that ending the bulk call records programme would increase the risk of a terrorist attack.

“I so regret what is happening; I will do everything I can to prevent this programme from being cancelled out,” she said.

Questions about what, if anything, the agency has been doing to track Americans’ movements using cellphone location data have been simmering for years. The issue flared up again after an ambiguous exchange between Mr Wyden and Gen Alexander at a Senate Intelligence Committee hearing last week.

Mr Wyden has been a critic of domestic surveillance programmes, and filed legislation in 2011 and again this year to require warrants for obtaining someone’s locational data in a criminal investigation. He has not disclosed what prompted his concerns.

At the hearing last week, Mr Wyden asked Gen Alexander “whether the NSA has ever collected or made any plans to collect Americans’ cell-site information in bulk”.

Gen Alexander replied that the NSA was not “receiving cell-site location data and has no current plans to do so” under Section 215 of the Patriot Act, which allows the secret surveillance court to issue orders for records from businesses — like telephone companies — if the records are “relevant” to an intelligence investigation.

But he also said last week that there was other classified information that the NSA had sent to the committee that provided “additional detail”.

In a 1979 case involving the small-scale collection of calling logs, the Supreme Court ruled that such records were not protected by constitutional privacy rights because people had already revealed the existence of their calls to telephone companies.

But in a 2012 case about the police’s use of a GPS tracker attached to a suspect’s car, five justices suggested that any long-term, automated collection of a person’s publicly displayed actions might raise privacy issues under the Fourth Amendment.

THE NEW YORK TIMES