The FBI has failed to review more than 8,000 hours of audio wiretap recordings related to counterterrorism investigations, a backlog that has more than doubled in size since last year, according to a new report issued yesterday.

The audit by Justice Department Inspector General Glenn A. Fine also found that although the FBI has made progress in improving its translation program, the bureau is still struggling to analyze recordings quickly enough and to hire and retain qualified translators.

"The success of the FBI's foreign language translation efforts is critical to its national security mission," the report said. It added that "key deficiencies remain, including a continuing amount of unreviewed material, instances where 'high priority' material has not been reviewed within 24 hours and continued challenges in meeting linguist hiring goals."

The new findings were released on the same day that FBI Director Robert S. Mueller III faced sharp questioning from members of the Senate Judiciary Committee, who complained at an oversight hearing that the FBI is not changing quickly enough to focus on terrorist threats and has bungled attempts to implement a $170 million computer upgrade.

"What happens if there's plans for an impending attack and we don't translate the audio until sometime after the attack?" asked Sen. Patrick J. Leahy (Vt.), the committee's ranking Democrat. ". . . I worry we're not moving fast enough to get those translated."

Mueller said the backlog in the review of audiotapes from counterterrorism and counterintelligence investigations involves less than 2 percent of all recordings and includes many tapes of "white noise from microphone recordings." Others consist of "obscure languages and dialects" that are difficult to translate, including one Mueller did not identify that could not be translated by anyone in the U.S. intelligence community, he said.

Justice Department investigators also found that it took the FBI an average of 16 months to hire contract linguists. Mueller said the problems are due in part to the rigorous hiring standards and the limited supply of applicants, who do not meet FBI qualifications 90 percent of the time.

"We understand that we have to make more progress and believe we're on track to do so in those areas pointed out by" Fine, Mueller told the committee.

Fine's report is the latest in a long series of critical reviews of the FBI, which is still struggling to refocus its mission of preventing terrorism nearly four years after the Sept. 11, 2001, attacks. In a shake-up last month, President Bush ordered the FBI to reorganize its intelligence program and to place much of it under the authority of the nation's new espionage chief, John D. Negroponte.

Senators from both parties focused much of their questioning yesterday on the continuing problems in the FBI's language and technology programs.

Mueller announced earlier this year that the FBI had to scrap a $170 million software upgrade because the program did not work. He said yesterday that it will be several years before a replacement can be ready. Mueller declined to provide the committee with a cost estimate for the new program, dubbed Sentinel, citing confidentiality rules governing the federal bidding process.

Mueller urged senators to give the FBI the power to issue administrative subpoenas -- a demand for documents that does not require a judge's approval -- in counterterrorism cases, arguing that it is already available in cases involving health care fraud, drugs, pornography and other crimes.

The Senate intelligence committee has endorsed such subpoena power in a bill renewing the USA Patriot Act counterterrorism law, but the Senate Judiciary Committee and the House have approved competing legislation that does not include the measure.