Greenwald, who has since left the Guardian for a yet-unnamed news site financed by Silicon Valley billionaire Pierre Omidyar, told Reuters he had nothing new to add to those statements, but reaffirmed the "precautions" Snowden took before leaving for Hong Kong.
Among the classified documents Snowden accessed, but not yet published, were lists of names and resumes of NSA and GCHQ employees, sources said.
Sources believe Snowden began downloading some of the material from a classified GCHQ website, GC-Wiki, when he was employed by Dell and assigned to the NSA in 2012. He moved to another contractor, Booz Allen Hamilton, because he would have more access to NSA data there, a source said.
No names of British intelligence officials have been published. Once UK authorities told the Guardian it could face legal action, the newspaper destroyed computers containing Snowden-provided documents on GCHQ, though it did give copies of the material to the New York Times and ProPublica.
Sources say the material Snowden took includes information, possibly personnel names, on the CIA and other US intelligence arms, such as the National Reconnaissance Center and the National Geospatial-Intelligence Agency.
Snowden's revelations of vast domestic and international surveillance and data collection by the US have made steady news since June. In addition to many storylines emanating from the leaks, the NSA's alleged spying on emails and tapping of phones of world leaders has provoked scandals between the US and a number of countries in Europe, Latin America and Asia.
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