WASHINGTON – Even before the White House formally authorized a secret program to spy on American citizens without obtaining warrants, such eavesdropping was occurring and some of the information was being shared with the FBI, declassified correspondence and interviews with congressional and intelligence officials indicate.

On October 1, 2001, three weeks after the September 11 terrorist attacks, General Michael Hayden, who was running the National Security Agency at the time, told the House intelligence committee that the agency was broadening its surveillance authorities, according to a newly released letter sent to him that month by Minority Leader Nancy Pelosi, a Democrat of California. Ms. Pelosi, the ranking Democrat on the committee, raised concerns in the letter, which was declassified with several redactions and made public yesterday by her staff.

“I am concerned whether and to what extent the National Security Agency has received specific presidential authorization for the operations you are conducting,” Ms. Pelosi wrote on October 11, 2001.The substance of General Hayden’s response one week later, on October 17, 2001, was redacted.

The secret NSA program, developed in the immediate aftermath of the attacks on Washington and New York as a way to find any hidden Al Qaeda operatives still in America, was authorized in October 2001, a senior administration official said.

The president and senior aides have publicly discussed various aspects of the program, but neither the White House, the NSA, nor the office of the director of national intelligence would say what day the president authorized it. An NSA spokesman, Don Weber, said in an e-mail yesterday that it would be inappropriate to “discuss details which could potentially cause harm to the safety of our nation.”

Ms. Pelosi’s letter suggested that she and others on the committee first heard about expanded work by the NSA on October 1, 2001, when General Hayden briefed them on NSA activities.

“During your appearance before the committee,” she wrote, “you indicated that you had been operating since the September 11 attacks with an expansive view of your authorities with respect to the conduct of electronic surveillance.” The letter, while redacted in parts concerned with surveillance, made clear that the agency was “forwarding” intercepts and other collected information to the FBI. Two sources familiar with the NSA program said Ms. Pelosi was directly referring to information collected without a warrant on American citizens or residents.

An intelligence official close to General Hayden said that his appearance on October 1, 2001, before the House committee had been to discuss Executive Order 12333, and not the NSA program.

The order, signed by President Reagan in 1981, gave guidance and specific instructions about the intelligence activities that the American government could engage in. It specifically prohibited domestic surveillance for intelligence purposes without a warrant “unless the Attorney General has determined in each case that there is probable cause to believe that the technique is directed against a foreign power or an agent of a foreign power.”