(CNN) -– The intelligence community has provided Congress additional counterterrorism justification for the government’s controversial stockpiles of telephone and Internet records.
Further, officials searched the database that holds telephone metadata fewer than 300 times last year, according to a document prepared by the intelligence community for members of Congress and provided to CNN by a congressional source.
The database is made up of billions of phone records the telephone companies are required to provide to the National Security Agency, and investigators use the data to assemble webs of who suspected terrorists have been in touch with. The NSA must delete records after five years, the letter says.
The government has said the data collected under the program - authorized by the Patriot Act and reviewed by the Federal Intelligence Surveillance Court - includes information such as a "telephone number or the length of a call," and the new document stresses the program "does not allow the government to listen to anyone's phone calls."
To search the data the NSA amasses, the document stresses investigators must have a "reasonable suspicion" and connect "an identifier," such as a name or telephone number, to "specific foreign terrorist organizations."
But privacy advocates have raised concerns over the program and also one that collects online communications. The existence of the programs, including a surveillance system known as PRISM that collects certain information from major technology companies including Google, Facebook, Microsoft and Yahoo, became known after a former National Security Agency and CIA contractor leaked information to two newspapers.
Taken together, "the intelligence gathered under them has contributed to the disruption of dozens of potential terrorist plots here in the homeland and in more than 20 countries around the world," the document said.
It provided no information about previously undisclosed attacks but noted the intelligence community is "working to be able to provide more information about this."
Senate Intelligence Committee Chairwoman Dianne Feinstein said some information could emerge in the coming days. She told reporters after a closed-door briefing on Thursday with National Security Agency Director Keith Alexander that "what he wants to give us are the cases where this has stopped a terrorist attack, both here and in other places. And he wants to be exact about the details. So we should have that Monday."
Other indications were that the information might be available later in the week.
The document, released ahead of the Sunday morning political talk programs, detailed how the phone records database was used in the case of Najibullah Zazi, who plotted to bomb the New York subway system.
Senior U.S. counterterrorism officials have previously told CNN that U.S. and British databases scooped up a September 2009 e-mail to Zazi by a sender connected to a suspected al Qaeda cell in Britain. U.S. Director of National Intelligence James Clapper has said communications intercepted in the Zazi case were critical in the investigation, which led to Zazi's 2010 guilty plea.
The document revealed investigators also used phone records collected under the program, "identifying and passing additional leads back to the FBI for investigation."
"One of these leads revealed a previously unknown number for co-conspirator Adis Medunjanin and corroborated his connection to Zazi as well as to other U.S.-based extremists," it read.
Previously, the intelligence community has cited e-mails collected in the Zazi case as a justification for the program, but some have since questioned whether the e-mails were obtained or could have been obtained through other avenues.
The programs are expected to be in the spotlight again on Sunday, when several current and former government officials are slated to appear on political programs.
House Intelligence Committee Chairman Mike Rogers will be interviewed on CNN's "State of the Union," as will Senate Foreign Relations Committee Chairman Robert Menendez. Glenn Greenwald, one of the reporters who broke the story, will appear on CNN's "Reliable Sources."
Also slated for Sunday morning interviews are former NSA and CIA Director Michael Hayden; former Vice President Dick Cheney; and Denis McDonough, the White House chief of staff. Rogers will also be interviewed on CBS.