"I think Congress has to carefully consider the powerful surveillance tools that we granted the government," Leahy said. "We have to ensure that there is stringent oversight, accountability and transparency."
Leahy, who chairs the Senate Judiciary Committee, said federal officials testifying at congressional hearings have admitted giving misleading statements on how effective NSA data collection has been.
Also Wednesday, the government released declassified documents that showed intelligence agents intercepted seven calls from a Sept. 11, 2001, hijacker before the attacks on the United States. National Intelligence Director James Clapper authorized the declassification and release of three documents "pertaining to the collection of telephone metadata" under the Patriot Act.
"DNI Clapper has determined that the release of these documents is in the public interest," the agency said in a release on the declassification of two letters concerning the reauthorization of the Patriot Act and a Foreign Intelligence Surveillance Court order.
In one document, a Dec. 4, 2009, letter concerning the Patriot Act reauthorization to the House Intelligence Committee, an attachment indicated "prior to the attacks of 9/11, the National Security Agency [NSA] intercepted and transcribed seven calls from hijacker Khalid al-Mihdhar to a facility associated with an al-Qaida safe house in Yemen. However, NSA's access point overseas did not provide the technical data indicating the location from where al-Mihdhar was calling. Lacking the originating phone number, NSA analysts concluded that al-Mihdhar was overseas. In fact, al-Mihdhar was calling from San Diego, California."
The December letter, which contained redacted material, said the Patriot Act allowed the bulk collection of "certain dialing, routing, addressing and signaling information about telephone calls and electronic communications ... that were communicating and the times and date but not the content of the calls or email messages themselves."
The data collection programs "operate on a very large scale," the letter read.
The second declassified document contained letters and attachments sent to the House and Senate intelligence committees when the Patriot Act was up for reauthorization in 2011.
The letters said the government obtained orders from different Foreign Intelligence Surveillance Court judges to operate the bulk collection programs.
"Before obtaining any information from a telecommunications service provider, the government must establish, and the FISA Court must conclude, that the information is relevant to an authorized investigation," the letters said.
On Tuesday, the Justice Department said it agreed to a review that could reveal how it orders technology firms to become part of NSA surveillance.
The department said it would complete a declassification review of binding surveillance orders on Yahoo! Inc. by Sept. 12. The review could be followed by their public release.
Information about the review came in a legal document the department sent to the secret U.S. Foreign Intelligence Surveillance Court in response to a Yahoo! lawsuit.
The document can be found at tinyurl.com/UPI-FISA-Court-Brief.
The lawsuit stemmed from an April 25, 2008, order by the FISA Court mandating Yahoo! comply with a clandestine mass electronic-surveillance order.
Yahoo! has recently been fighting for increased transparency surrounding mass-surveillance orders after disclosures by NSA secrets leaker Edward Snowden.
The Justice Department will complete an additional declassification review of "briefs and materials" linked to the April 2008 ruling by Sept. 27, acting Assistant Attorney General for National Security John Carlin told presiding FISA Judge Reggie Walton in the legal brief.
Walton separately told Senate Judiciary Committee Chairman Patrick Leahy, D-Vt., in a letter Monday Yahoo! was the only recipient of a bulk-surveillance order to plead its case before the FISA Court after it refused to comply with 2007 surveillance directives.
That refusal prompted the court to issue the 2008 order Yahoo! wants declassified.
"Yahoo! refused to comply with the directives, and the government filed a motion with this court to compel compliance," Walton wrote in the letter. "The court ordered and received briefing from both parties, and rendered a decision in April 2008."
Walton's letter can be found at tinyurl.com/UPI-FISA-Leahy-Letter.
Leahy is sponsoring a bill to shorten the lifespan of the USA Patriot Act and end bulk surveillance altogether. He also advocates increased transparency around key FISA Court rulings.