Lawmakers voiced their confusion and concern, and some called for the end of sweeping surveillance programs by US spy agencies after receiving an unusual briefing on the government's yearslong collection of phone records and Internet usage.
The phalanx of FBI, legal and intelligence officials who briefed the entire House was the latest attempt to soothe outrage over National Security Agency programs that collect billions of Americans' phone and Internet records.
Since they were revealed last week, the programs have spurred distrust in the Obama administration from around the world.
Congressional leaders and intelligence committee members have been routinely briefed about the spy programs, officials said, and Congress has at least twice renewed laws approving them.
But the disclosure of their sheer scope stunned some lawmakers, shocked foreign allies from nations with strict privacy protections and emboldened civil liberties advocates who long have accused the government of being too invasive in the name of national security.
Some congressmen admitted they'd been caught unawares by the scope of the programs, having skipped previous briefings by the intelligence committees.
"I think Congress has really found itself a little bit asleep at the wheel," Democratic Rep. Steve Cohen of Tennessee said.
Many leaving the briefing declared themselves disturbed by what they'd heard and in need of more answers.
"Congress needs to debate this issue and determine what tools we give to our intelligence community to protect us from a terrorist attack," said Rep. C.A. Dutch Ruppersberger of Maryland, top Democrat on the House Intelligence Committee, and a backer of the surveillance.
"Really it's a debate between public safety, how far we go with public safety and protecting us from terrorist attacks versus how far we go on the other side."
He said his panel and the House Judiciary Committee will examine what has happened and see whether there are recommendations to be made for the future.
The Senate Appropriations defense subcommittee will get to question the head of the NSA, Gen. Keith Alexander today and the Senate and House intelligence committees will be briefed on the programs again Thursday.
The country's main civil liberties organization wasn't buying the administration's explanations, filing the most significant lawsuit against the massive phone record collection program so far.
