A United States intelligence agency has formally requested a criminal probe into the leak of highly classified information about secret surveillance programmes run by the National Security Agency.
A "crimes report" asking for the inquiry, which will go to the U.S. Justice Department, was filed by the super-secret NSA.
Officials said an investigation will undoubtedly try to uncover the leaker who gave a secret court order to Britain's Guardian newspaper.
It will also try to find out who gave a document describing surveillance methods to both the Guardian and the Washington Post.
U.S. Director of National Intelligence James Clapper has blamed the outlets for what he has called "reckless disclosures" of classified spy agency material.
It is not known how broad a leaks investigation has been requested by the NSA and a Justice Department spokesman has declined to comment.
The Justice Department has established procedures for determining whether an investigation is warranted and prosecutors do not accept all requests.
U.S. officials said the NSA leaks were so astonishing they expected the Justice Department to take the case.