ATLANTA — The FBI obtained a search warrant to seize hundreds of boxes of ballots from election offices in Fulton County, Ga., as part of a criminal investigation into alleged “deficiencies or defects” in the vote count in the 2020 contest lost by President Trump, according to an affidavit unsealed Tuesday.

The affidavit provides the first public justification for an FBI search last month that targeted a county that Trump and allies have long seen as central to their false claim that the 2020 election was stolen. The investigation, based on a referral from a Trump administration official, rests on claims that have long been made by people who assert widespread fraud in the contest even though audits, state officials, courts and Trump’s own former attorney general have all rejected the idea of widespread problems that could have altered the outcome.

The investigation began with a referral from Kurt Olsen, who served as Trump’s 2020 campaign lawyer when it lost dozens of lawsuits challenging the election and now serves as an administration official overseeing the attempt to investigate Trump’s loss, according to the affidavit.

The search of the heavily Democratic county stirred immediate concerns among Democrats that Trump was marshaling the powers of the FBI and Justice Department to pursue retribution over his persistent claims of a stolen election and because of the unusual presence of Tulsi Gabbard, the country’s director of national intelligence. The affidavit makes no mention of any evidence of foreign interference in the 2020 election even though the possibility of such meddling has been a long-standing conspiracy theory among Trump supporters who question the 2020 vote count.

Democrat Joe Biden won Georgia by about 11,800 votes in an election overseen by a Republican secretary of state and certified by a Republican governor.

Among the “deficiencies or defects” investigators are looking at is Fulton County’s admission that it does not have scanned images of all the ballots counted during the original count or the recount, according to the affidavit. Fulton County has also confirmed that some ballots were scanned multiple times during the recount, the affidavit says.

“If these deficiencies were the result of intentional action, it would be a violation of federal law regardless of whether the failure to retain records or the deprivation of a fair tabulation of a vote was outcome determinative for any particular election or race,” the document says.

The affidavit says seizures of the election records was necessary to determine whether election records were destroyed and or the tabulation of votes included materially false votes.” It cites potential violations of a law regarding the preservation and retention of election records, a misdemeanor. It also cites a law that makes it a crime to “knowingly and willfully” deprive residents of a “fair and impartially conducted election process,” which is a felony.

But the document also expresses uncertainty about whether the potential defects constitute a crime, noting that elections in Fulton County have already been the subject of multiple reviews.

After a particularly disastrous primary election in 2020, an independent monitor was hired to observe the general election that year as part of an agreement between the county and the State Election Board. He documented “sloppy processes” and “systemic disorganization” but found no evidence of illegality or fraud.

State lawmakers in 2021 used a provision of a new law to initiate a performance review of the county’s election practices. That review found that the county’s elections had been characterized by “disorganization and a lack of a sense of urgency in resolving issues.” But it also found the county had shown marked improvement.

An investigation by the secretary of state’s office and a performance review by the state elections board, which came at the urging of the Republican-controlled Legislature, came to similar conclusions.

According to the affidavit, the review board stated, “we do not see any evidence of fraud, intentional misconduct, or large systematic issues that would have affected the result of the November 2020 election.”

Agents armed with a warrant spent hours on Jan. 28 at the country elections hub, just sought of Atlanta, before driving off with trucks loaded with hundreds of cartons of election materials.

A week after the seizure, Fulton County officials filed a motion seeking the return of the materials that had been taken and the unsealing of the sworn statement presented to the judge who signed off on the search. The warrant sought the seizure of the following documents related to the 2020 election in the county: all ballots, tabulator tapes from the scanners that tally the votes, electronic ballot images created when the ballots were counted and then recounted, and all voter rolls.

“Claims that the 2020 election results were fraudulent or otherwise invalid have been exhaustively reviewed and, without exception, refuted,” the county argued in a court filing, noting that numerous lawsuits, as well as state and federal investigations, had found no evidence of fraud.

Brumback, Tucker and Durkin Richer write for the Associated Press. AP writer Nicholas Riccardi in Denver contributed to this report.