Federal agents building case against Snowden while White House claims to welcome debate on elec. surveillance – Joe Johns reports

FROM CNN WIRES:

The White House said Monday it welcomes a debate over the electronic surveillance programs exposed by a National Security Agency contractor, even as federal agents began building a case against the self-proclaimed leaker.

Edward Snowden told the British newspaper the Guardian that he left behind his family and a six-figure job in Hawaii to reveal the extent of the NSA's collection of telephone and Internet data, which he called "an existential threat to democracy." The 29-year-old worked for computer consultant Booz Allen Hamilton, a contractor for the U.S. electronic intelligence agency.

Snowden said he expects to be prosecuted for the leak, and a federal law enforcement official said Monday that FBI agents have begun an investigation by searching the 29-year-old's home and computers and seeking interviews with his girlfriend, relatives, friends and co-workers.

READ MORE: Feds start building case against NSA leaker