WASHINGTON — The Justice Department inspector general has found evidence that an FBI employee may have altered a document connected to court-approved surveillance of a former Trump campaign adviser, but has concluded that the conduct did not affect the overall validity of the surveillance application, according to U.S. officials familiar with the matter.

The person under scrutiny has not been identified but is a low-level FBI lawyer who has since been forced out of the FBI, according to the officials, who spoke on the condition of anonymity to discuss material that has not yet been made public.

The allegation is contained in a draft of Inspector General Michael Horowitz's report analyzing the FBI's Russia investigation, which witnesses have in recent weeks been allowed to review, people familiar with the matter said. The report is scheduled to be released publicly Dec. 9.

The employee was forced out of the FBI after the incident was discovered, two U.S. officials said. Horowitz found that the employee erroneously indicated he had documentation to back up a claim he had made in discussions with the Justice Department about the factual basis for the application. He then altered an email to back up that erroneous claim, they said.

That conduct did not alter Horowitz’s finding that the surveillance application of former Trump campaign adviser Carter Page had a proper legal and factual basis, the officials said.

Horowitz has been exploring various aspects of the Russia probe but was focused in particular on applications the FBI filed with the Foreign Intelligence Surveillance Court to monitor Page’s electronic communications.

The alleged alteration of a document by an FBI employee was first reported by CNN.

Separately, Attorney General William Barr tapped U.S. Attorney John Durham to explore the origins of the FBI probe and U.S. intelligence agency activities aimed at the Trump campaign, and Durham is expected to pursue the allegation surrounding the altered document to see whether it constitutes a crime, people familiar with the matter said.

Durham's work is expected to continue well after publication of the inspector general's report.

A spokeswoman for the inspector general declined to comment, as did a spokeswoman for the FBI. A spokeswoman for the Justice Department did not respond to a request for comment.

President Donald Trump and fellow Republicans have been clamoring for the report’s release, particularly as House Democrats have held high-profile impeachment hearings this month.

Sen. Lindsey Graham, R-S.C., chairman of the Senate Judiciary Committee, said the panel plans to hold a hearing with testimony from Horowitz on Dec. 11.

The inspector general has been investigating how the FBI pursued allegations of collusion and conspiracy between Trump associates and Russian agents during the 2016 election.

In recent weeks, key witnesses in the investigation have been called in to review and comment on sections of the report. The Washington Post reported last week that, unlike in previous inspector general reports, witnesses were told they could not submit written responses to the report, which remains a classified document. That raised alarms among some witnesses worried they would not be allowed to correct errors or misunderstandings in the report, according to people familiar with the matter.

After The Post's report, the inspector general's office clarified to witnesses that they would be allowed to submit written comments.

Democrats and Republicans have eagerly awaited release of the report, hopeful that the Justice Department's internal watchdog will validate their views on the law enforcement investigation that dogged the first two years of Trump's presidency.

Conservatives have alleged that a medley of wrongdoing occurred during the investigation, which was eventually taken over by special counsel Robert Mueller III, and they are likely to seize on any criticism that Horowitz directs at those involved in the probe. Some Trump supporters have referred to the investigation as an attempted "coup."

Mueller issued a lengthy report this year concluding there was insufficient evidence to support charges of conspiracy between any Trump associates and Russian agents. Mueller also elected not to decide whether the president had obstructed justice in the course of the inquiry, though Barr reviewed Mueller’s findings and concluded the president had not broken the law.

Democrats, meanwhile, are hopeful Horowitz will disprove various conspiracy theories that have been offered about the case and refute Trump’s assertion that Mueller’s probe was a “witch hunt” tainted by political bias against the president.