Facing criticism in both parties over surveillance work by the National Security Agency, intelligence officials released a series of top secret documents on how the NSA accesses bulk telephone records for terrorism investigations, as lawmakers demanded tighter restrictions to prevent civil liberties violations.

"In the interest of increased transparency, the Director of National Intelligence has authorized the declassification and public release of the attached documents pertaining to the collection of telephone metadata pursuant to Section 215 of the PATRIOT Act," read a statement issued by Director of National Intelligece James Clapper.

"DNI Clapper has determined that the release of these documents is in the public interest," the statement added.

There are three different items made public today that authorized the collection of telephone records:

The "Primary Order for Business Records Collection" is a secret court order made by the special intelligence court - you will notice that parts of the 18 pages are blacked out.

"We welcome a public debate about how best to safeguard both our national security and the privacy of our citizens," said Deputy Attorney General James Cole.

At a Senate hearing, most of the sparring between officials and Senators was about the Section 215 powers under the Patriot Act to access phone records, which has drawn opponents in both parties.

Intelligence officials again said that Patriot Act authority was an important tool in their work.

There were also questions today on how the NSA leaks happened.

"How soon will we know who screwed up?" asked Sen. Patrick Leahy (D-VT), the Chairman of the Senate Judiciary Committee, who was told the investigation into Edward Snowden's leaks should produce answers in the "weeks and months" ahead.