WASHINGTON - A Senate panel wants to know if the Patriot Act needs to be revised to keep the FBI from illegally or improperly gathering telephone, e-mail and financial records of Americans and foreigners while pursuing terrorists.

FBI Director Robert Mueller was to testify Tuesday before the Senate Judiciary Committee. It was the panel's second hearing into a report earlier this month by the Justice Department inspector general that revealed abuses in the FBI's use of documents called national security letters to gather data.

The committee plans to hear April 17 from Attorney General Alberto Gonzales, who is struggling to keep his job amid criticism of the NSL abuses and the firings of eight U.S. attorneys.

"Last year the administration sought new powers in the Patriot Act to appoint U.S. Attorneys without Senate confirmation and to more freely use National Security Letters," Senate Judiciary Chairman Patrick Leahy, D-Vt., said in remarks prepared for Tuesday's hearing. "The administration got these powers, and they have badly bungled both."

In a review of headquarters files and a sampling of four of the FBI's 56 field offices, Inspector General Glenn A. Fine found 48 violations of law or presidential directives during 2003-2005. He estimates there may be as many as 3,000 violations throughout the FBI that have not been identified or reported.

"I am to be held accountable," Mueller said when the report came out. He ordered an audit of all 56 FBI field offices to determine the extent of the problem.

But Mueller also tried to head off any reduction in the bureau's authority to use such letters, which he called "the bread and butter of our investigations."

Congress is less certain.

When Fine testified before the Senate panel last week, Leahy said, "In light of this report, we need to consider whether Congress went too far" in the Patriot Act in removing restrictions on FBI use of national security letters.

In a House Judiciary Committee hearing with Fine, Republicans and Democrats warned the FBI could lose that broad power.

If the FBI doesn't move swiftly to correct the mistakes and problems, "you probably won't have NSL authority," said Rep. Dan Lungren, R-Calif., a supporter of the power.

In 1986, Congress first authorized FBI agents to obtain electronic records without approval from a judge, using national security letters.

The letters can be used to acquire e-mails, telephone, travel records and financial information, like credit and bank transactions. They can be sent to telephone and Internet access companies, universities, public interest organizations, nearly all libraries, financial and credit companies.

In 2001, the Patriot Act eliminated any requirement that the records belong to someone under suspicion. Now an innocent person's records can be obtained if FBI field agents consider them relevant to an ongoing terrorism or spying investigation.

In 2000, the FBI issued an estimated 8,500 requests. That number peaked in 2004 with 56,000. Overall, the FBI reported issuing 143,074 requests in national security letters between 2003 and 2005. In 2005, 53 percent were for records of U.S. citizens or permanent residents.

Rep. Jerrold Nadler, D-N.Y., said Congress should revise the Patriot Act. "It is not enough to mandate that the FBI fix internal management problems and record keeping, because the statute itself authorizes the unchecked collection of information on innocent Americans," Nadler said.