Facing a global uproar over the operations that track phone and internet messages around the world, the Justice Department continued to investigate whether the disclosures of Snowden, 29, an employee of government contractor Booz Allen Hamilton, were criminal.
The journalist who exposed the surveillance programmes said that there will be more “significant revelations” to come from the documents.
“We are going to have a lot more significant revelations that have not yet been heard over the next several weeks and months,” said Glenn Greenwald of the Guardian. “There are dozens of stories generated by the documents he provided, and we intend to pursue every last one of them.”
Meanwhile, the European Parliament planned to debate the spy programmes and whether they have violated local privacy protections.
Snowden has disappeared under the radar after fleeing to Hong Kong in the hope of escaping criminal charges, as politicians accuse him of committing an “act of treason” that should be prosecuted.
A senior US intelligence official said there were no plans to scrap the programmes that, despite the backlash, continue to receive widespread if cautious support within Congress.
The programmes were revealed last week by the Guardian and the Washington Post newspapers.
National Intelligence director James Clapper has taken the unusual step of declassifying some of the previously top-secret details to help the administration mount a public defence of the surveillance as a necessary step to protect Americans.
One of the National Security Agency programmes gathers hundreds of millions of US phone records to search for possible links to known terrorist targets abroad. The other allows the government to tap into nine US internet companies and gather all communications to detect suspicious behaviour that begins overseas.
Snowden is a former CIA employee who later worked as a contractor for the NSA on behalf of Booz Allen, where he gained access to the surveillance.
The first explosive document he revealed was a top secret court order issued by the Foreign Intelligence Surveillance Court that granted a three-month renewal for a massive collection of American phone records. That order was signed April 25.
He also gave the Post and Guardian a PowerPoint presentation on another secret programme that collects online usage by the nine internet providers. The US government says it uses that information only to track foreigners’ use overseas.
Believing his role would soon be exposed, Snowden fled last month to Hong Kong.
Meanwhile, Lindsay Mills, the 28-year-old girlfriend of Snowden, says she feels adrift without her boyfriend, who told her he would be leaving her for a few weeks for work, but abandoned her in Hawaii to hide in Hong Kong.
“My world has opened and closed all at once. Leaving me lost at sea without a compass,” Mills, a professional pole dancer, wrote on her blog, L’s Journey.
“As I type this on my tear-streaked keyboard I’m reflecting on all the faces that have graced my path,” Mills continued. “The ones I laughed with. The ones I’ve held. The one I’ve grown to love the most. And the ones I never got to bid adieu. But sometimes life doesn’t afford proper goodbyes.”
“Surely there will be villainous pirates, distracting mermaids, and tides of change in this new open water chapter of my journey,” Mills added. “But at the moment all I can feel is alone.”