WASHINGTON — FBI searches for Americans’ information that is collected using a high-profile surveillance tool have “dramatically decreased” since summer 2021, when the bureau overhauled its system after a judge accused it of widespread violations, according to a new government report.

The four-page report also provides new details about internal efforts over the past two years to tighten constraints on FBI queries for information about Americans in a repository of communications gathered by a warrantless surveillance program. The New York Times obtained a copy of the report, which has not been made public, after Justice Department officials sent it to Congress this week as they lobby lawmakers to extend the law that authorizes the program.

Known as Section 702, the surveillance law will expire at the end of the year unless Congress enacts new legislation. National security officials call it a critical tool for a range of foreign intelligence gathering, but its renewal is expected to face steep political headwinds. Civil libertarians have long been critical of Section 702 and have been joined by Republicans aligned with former President Donald Trump, who has promoted skepticism of security agencies and surveillance.

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Section 702 grew out of a once-secret warrantless wiretapping program started by the George W. Bush administration after the 9/11 terrorist attacks. It allows the government to collect — on domestic soil and without a warrant — the messages of targeted foreigners abroad, even when they interact with Americans.

The program has drawn controversy because analysts at intelligence agencies and the FBI can search the repository of intercepted messages using identifiers of Americans — like names, phone numbers and email addresses — even though that information was collected without a warrant.

How often the FBI searches for Americans’ information in the 702 repository has been murky. The bureau resisted making an estimate for years, saying that its systems — which allow agents to search many databases at once when hunting for data relevant to foreign intelligence or a crime — could not produce a reliable number.

Forced to try, the FBI last year estimated fewer than 3.4 million searches for 2021, up from fewer than 1.9 million the previous year. But the value of those numbers was not clear for multiple reasons, including how searches are tallied. A so-called batch inquiry that uses identifiers for 99 foreigners and one American, for instance, is counted as 100 searches for Americans’ data.

While the unclassified report said the number of queries for Americans’ information “dramatically decreased after FBI implemented its reforms beginning in the summer of 2021,” it did not specify what the more recent figures were.

A senior FBI official separately characterized the drop in query numbers as a “substantial decline” in a statement to the Times but declined to identify the 2022 estimate, saying the number was classified. But the official said the Office of the Director of National Intelligence is expected to disclose that number next month as part of an annual transparency report about the government’s use of surveillance.

In a speech urging the reauthorization of Section 702 at the Brookings Institution on Tuesday, Matthew Olsen, the chief of the department’s national security division, also said there had been “a dramatic decrease” in the total number of FBI queries about Americans and a “significant reduction” in the number of inadvertent queries since the 2021 changes.

There are rules that limit when analysts can search the warrantless surveillance repository. At the FBI, for example, analysts can use Americans’ identifiers to search the database only if there is a reason to believe it will return information about foreign intelligence or evidence of a crime.

But FBI agents have repeatedly violated those constraints and searched for other purposes, such as vetting maintenance workers or potential informants. A recent report disclosed that one bureau analyst used the name of a member of Congress to search the repository without sufficient “limiters” to focus results on the task at hand.

In rulings made public in 2020 and 2021, the chief judge of the Foreign Intelligence Surveillance Court, James Boasberg, declared that the bureau had committed “apparent widespread violations of the querying standard.”

But he also allowed the program to continue operating because the FBI said it would change its systems and training to reduce the problems, while noting that “ongoing monitoring and auditing will be critical to evaluating whether the current measures are adequate.”

The report says that in an opinion in April 2022 that reapproved the program for another year, the surveillance court praised the improvements. The court was quoted as saying it was “encouraged” by the changes the FBI had made and that “there are preliminary indications that some of these measures are having the desired effect.”

That opinion remains classified, leaving it unclear whether the court had any criticisms.

In August 2020, William Barr, the attorney general at the time, ordered more auditing at the FBI to reduce the frequency of violations of various kinds of foreign intelligence surveillance.

In an April 2021 memo that the department provided to Congress this week and that the Times also obtained, Attorney General Merrick Garland asked for more compliance measures with a further order that the department also provided to Congress this week and which the Times also obtained.

The report described several changes to the FBI’s systems since June 2021, which it said were carried out under the deputy attorney general, Lisa Monaco.

To “address the large number of inadvertent queries,” the 702 repository is now excluded by default when FBI officials go to search the bureau’s databases for information, and searchers must opt in to query it. That change alone, the report said, “not only decreased the number of U.S. person queries overall but has also greatly reduced the number of inadvertent queries.”

Analysts must now obtain advance approval from an FBI lawyer before conducting a “batch” query of the 702 repository that uses more than 100 identifiers all at once.

The idea, the report said, was to ensure greater review in a situation “where one incorrect decision could potentially have a greater privacy impact due to the large number of query terms.” Since that change, the “FBI appears to be conducting fewer ‘batch job’ queries, which has further reduced the number of U.S. person queries,” and there have been no further violations of the querying standards identified for large batch inquiries, the report said.

At the surveillance court’s direction, the FBI also requires agents to write an audited “case-specific justification” for every query about an American. Previously, the report said, the system would automatically fill in a generic justification.

In March 2022, the report said, the bureau required analysts to get a lawyer’s permission before making certain “sensitive” queries about Americans, including “those involving elected officials, members of the media, members of academia or religious figures.”

The report also said the FBI deputy director must personally approve certain particularly sensitive queries, although it was unclear what qualified.

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