The FBI did not closely follow the rules for verifying claims when its agents applied for court permission to conduct secret surveillance, according to a preliminary audit by the Justice Department's inspector general.

The review examined the FBI's applications under the Foreign Intelligence Surveillance Act, or FISA, in terrorism and counterintelligence investigations. Inspector General Michael Horowitz issued a highly critical report in December concluding that the FBI made serious mistakes in applying for a FISA warrant to surveil Carter Page, a former Trump campaign adviser.

The Page case raised the question of whether the mistakes were widespread. The latest review suggests they were. The FBI and Justice Department said they have since made changes in the process to eliminate those problems.

Horowitz said Tuesday that an audit of 29 FISA applications from eight FBI field offices over the past five years showed a lack of compliance with the requirement that their factual allegations be properly documented, as required by what are known as Woods Procedures for review of accuracy.

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"We do not have confidence that the FBI has executed its Woods Procedures in compliance with FBI policy," he wrote.

The audit was conducted on FISA applications submitted between October 2014 and September 2019 to surveil people in the United States. The FBI couldn't locate the Woods files for four of the 29 applications and didn't know whether three of those four files ever existed, according to the audit, and the other 25 files contained apparent errors or inadequate supporting facts.

Horowitz said he made no judgement about whether the mistakes were material or whether the necessary backup information could be found in the case files or elsewhere.

"We do not speculate as to whether the potential errors would have influenced the decision to file the application or the [court's] decision to approve the FISA application," he wrote.

But he said the audit showed the FBI is not living up to its goal of being "scrupulously accurate" in FISA applications.

The FISA warrants are effective for up to 90 days, and the FBI must resubmit an application if it wants to continue the surveillance. Tuesday's audit said agents are "not consistently re-verifying the original statements of fact" when they seek renewal. That problem was a prominent finding in the December inspector general report on the Page warrants.

In a response included in the inspector general's findings — a "management advisory memorandum," not a full report — the FBI said the changes instituted by Director Christopher Wray, ordered as a result of the IG report on the Carter Page FISA warrant, addressed these issues. The Justice Department said the audit "did not examine any FISA applications filed after implementation of the reforms" ordered by Wray. It called the FISA process "an essential tool to guard against terrorism and other national security threats."

The congressional authorization to seek the secret warrants expired March 15, and the fallout from the handling of the Carter Page FISA has made renewal a controversial issue. After extensive lobbying by Attorney General William Barr, the Senate passed a bill to renew the authorization, but the House left town without taking action.

The FISA authority remains in effect for investigations that were underway when the law expired or for new cases based on events that took place before the expiration date.

The American Civil Liberties Union, which has pushed Congress to make changes in the process, said the findings validate its longstanding concerns about the FISA law.

"This report further demonstrates that the incident with Carter Page was not a one-off," the organization said. "There are systemic problems with our foreign intelligence surveillance laws and courts."