US Director of National Intelligence James Clapper confirms this through a letter.
The US National Security Agency (NSA) used a loophole in surveillance laws to carry out warrantless searches on American communications such as call and e-mail data, according to the US Director of National Intelligence James Clapper.
In a letter to Sen. Ron Wyden (D-OR), which was seen by The Guardian, Clapper noted that have been queries, using US person identifiers, of communications lawfully acquired to obtain foreign intelligence targeting non-U.S. persons reasonably believed to be located outside the United States.
"These queries were performed pursuant to minimisation procedures approved by the FISA court and consistent with the statute and the fourth amendment," Clapper said.
However, he did not reveal how many US nationals were affected by these searches.
With this statement, this is the first time Clapper has admitted publicly the NSA conducted such searches by exploiting a loophole in surveillance law.
Whistleblower Edward Snowden revealed that NSA conducted the searches through controversial programmes such as Prism and Upstream.
Prism enables the agency to collect data from Google, Apple, Facebook, Yahoo and other technology firms, while the Upstream programme is a network of internet cable taps.