For almost three years the National Security Agency has been tapping the data it collects to map out some Americans' social connections, allowing the government to identify their associates, their locations at certain times, their traveling companions and other personal information, The New York times reported.

Citing documents provided by former NSA systems analyst Edward Snowden, the Times reported that the NSA began allowing the analysis of phone call and e-mail logs in November 2010 to examine some Americans' networks of associations for foreign intelligence purposes after NSA officials lifted restrictions on the practice. The newspaper posted the report on its website Saturday.

A January 2011 memorandum from the spy agency indicated that the policy shift was intended to help the agency "discover and track" connections between intelligence targets overseas and people in the United States, the Times reported.

The documents Snowden provided indicated that the NSA can augment the communications data with material from public, commercial and other sources, including bank codes, insurance information, Facebook profiles, passenger manifests, voter registration rolls and GPS location information, as well as property records and unspecified tax data, the paper reported.

NSA officials declined to say how many Americans have been caught up in the effort, including people involved in no wrongdoing, the Times reported. The documents do not describe what has resulted from the scrutiny, which links phone numbers and e-mails in a "contact chain" tied directly or indirectly to a person or organization overseas that is of foreign intelligence interest, the paper reported.

The documents provided by Snowden don't specify which phone and e-mail databases are used to create the social network diagrams, the Times reported, and NSA officials wouldn't identify them. However, NSA officials said the large database of Americans' domestic phone call records revealed in June was not used, the paper reported.

Disclosures from documents leaked by Snowden earlier this year have sparked debate over the government's surveillance activities and concerns that Americans' civil liberties have been violated by the data collection. Russia has granted temporary asylum to Snowden, considered a fugitive from justice in the U.S., and his whereabouts remain secret.