The?Obama administration on Wednesday?officially?declassified three?files to?offer details to the National Security Agency's phone surveillance program, before Senators grilled intelligence officials about the program in a hearing.

The sweeping phone surveillance program, code-named Prism,?is one of the two secret surveillance programs revealed in June by former government contractor Edward Snowden,?who has filed?asylum?to Russia.

U.S. Director of National Intelligence James Clapper on Wednesday authorized the declassification and public release of three documents that outline the limits, oversight and utility of the surveillance program which have collected phone call records within the United States.

According to a statement by the office of National Intelligence, Clapper has determined that "the release of these documents is in the public interest."

The newly declassified documents include a Foreign Intelligence Surveillance Act (FISA) Court order to an unnamed company, requiring it to produce "all call detail records" on an "ongoing daily basis."

The records include phone numbers, call times and duration, but have no contents of the conversation.

The court order allowed only authorized NSA officials to access the phone data, and allowed the program to store data for five years.

Another declassified document, a letter written in 2009 concerning the Patriot Act reauthorization to the House Intelligence Committee, tried to indicate that these surveillance programs could play an important role in counter-terrorism efforts.

"Prior to the attacks of 9/11, the National Security Agency intercepted and transcribed seven calls from hijacker Khalid al- Mihdhar to a facility associated with an al-Qaeda 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 declassification of three documents came the same day as the Senate Judiciary Committee held a hearing over the phone calls scooping program.

Officials of the Obama administration and the intelligence community have repeatedly defended the surveillance programs by emphasizing that they have been a useful counter-terrorism tool.

However, several lawmakers remained skeptical about the utility of the phone surveillance program during Wednesday's hearing.

Senator Patrick Leahy, chairman of the Senate Judiciary Committee, said that he was not convinced that the telephone metadata program has been critical to the effort to disrupt terrorist plots.

"I think Congress has to carefully consider the powerful surveillance tools that we granted the government. We have to ensure that there is stringent oversight, accountability and transparency," said Leahy.

Senator Dianne Feinstein, who chairs the Senate Intelligence Committee, said she supported the phone surveillance program but added "that doesn't mean that we can't make some changes."

She and other lawmakers also floated some idea of changes to the phone surveillance program, including reducing the five-year retention period that the intelligence community could keep the phone records in its database and limiting the scope of the metadata collection.