The Obama administration expressed heightened alarm today over fugitive leaker Edward Snowden’s stash of secret spy files, as a new batch of highly classified papers spilled across the Internet, revealing how the U.S. government collected online data in bulk.

A top aide to President Obama conceded that the administration doesn’t know yet all of what Snowden allegedly swiped while he was a National Security Agency contractor before he slipped to Hong Kong earlier this month and then to Moscow.

“Look, I don’t know with certainty what Mr. Snowden has,” Deputy National Security Advisor Ben Rhodes told reporters in Dakar, Senegal. “That’s something that we’re actively seeking to determine.”

Snowden has already compromised “very classified programs” by leaking them to three newspapers and by taking files overseas, Rhodes said, acknowledging that the government still believes he’s carrying the files on his person.