NEW YORK — Eric Adams, a retired police captain who was elected as New York City’s 110th mayor nearly three years ago on a promise to rein in crime, has been indicted following a federal corruption investigation, people with knowledge of the matter said Wednesday.

The indictment remained sealed Wednesday night, and it was unclear what charge or charges Adams would face. But the federal investigation has focused at least in part on whether Adams and his campaign conspired with the Turkish government to receive illegal foreign donations.

When the indictment is made public, Adams will become the first New York City mayor to face a federal charge while in office.

The indictment promised to reverberate across the nation’s largest city and beyond, plunging Adams’ embattled administration further into chaos just months before he is set to face challengers in a hotly contested mayoral primary.

In a statement, Adams said he had done nothing wrong.

“I always knew that if I stood my ground for New Yorkers that I would be a target — and a target I became,” he said. “If I am charged, I am innocent and I will fight this with every ounce of my strength and spirit.”

Brendan R. McGuire and Boyd M. Johnson III, partners at WilmerHale who represent the mayor, did not immediately respond to requests for comment.

Representatives of the U.S. attorney’s office for the Southern District of New York, the FBI and the city’s Department of Investigation declined to comment.

The indictment represented an extraordinary turnabout for Adams, 64, a former state senator and Brooklyn borough president who took office as the city was rebounding from the pandemic and about to confront a massive influx of migrants from the southern border.

It grew out of an investigation by the FBI and federal prosecutors in Manhattan that began more than two years ago and was focused at least in part on the possible foreign donations, and on whether Adams pressured officials in the Fire Department to sign off on the opening of a new high-rise consulate building for the Turkish government despite safety concerns. The investigators were also examining whether Adams accepted pricey flights and upgrades on Turkish Airlines, which is partly owned by the Turkish government.

The inquiry remained secret until late last year, when an FBI search of his chief fundraiser’s home thrust it into public view. After searching the home of the fundraiser, Brianna Suggs, last November, federal investigators left with two laptop computers, three iPhones and a manila folder labeled “Eric Adams.” Suggs has not been accused of wrongdoing.

Days later, in a dramatic scene on a Greenwich Village street, FBI agents told the mayor’s security detail to step aside, climbed into his SUV with him and seized his electronic devices.

Until federal investigations closed in on him, Adams’ life had seemed a classic New York success story.

Raised by a working-class mother in Brooklyn and Queens, he overcame dyslexia and run-ins with the police, and then joined the Police Department himself. He worked initially as a transit officer, and sought to make changes from within. During a two-decade career there, he rose to the rank of captain and served as a vocal, and sometimes contentious, advocate for Black officers.

Retiring to pursue a life in politics, Adams dreamed for years of becoming New York’s mayor, an ambition he realized by embracing diverse constituencies across the city, and an accomplishment he has said was divinely ordained.

As mayor, Adams vowed to return “swagger” to a city still emerging from the pandemic, and he surrounded himself in City Hall with friends and associates whose loyalty to him sometimes exceeded their policy expertise. Several had troubled pasts.

But his 33-month tenure as mayor has been marred by scandal. In July 2023, Manhattan District Attorney Alvin Bragg charged six people, including a retired police inspector who had worked and socialized with Adams, with conspiring to funnel illegal donations to the mayoral campaign.

Two months later, Bragg charged Eric Ulrich, the mayor’s former senior adviser and buildings commissioner, with conspiracy and taking bribes. Bragg accused Ulrich of using his city-funded position to “line his pockets.”

More recently, federal agents seized the phones of some of the highest-ranking officials in city government, including the police commissioner, the schools chancellor, the first deputy mayor, the deputy mayor for public safety, and a senior adviser who has been sued four times this year for sexual harassment. None of those officials has been charged with a crime.

Although he will become the first sitting mayor to be criminally charged, Adams is hardly the first to face criminal investigation. Jimmy Walker, a flamboyant, nightlife-loving mayor known as Beau James, held court in Jazz Age New York City but resigned amid a corruption scandal and fled to Europe.

Mayor William O’Dwyer, the only modern mayor aside from Adams to have served as a police officer, resigned months into his second term amid what was described in his obituary as “the biggest police scandal in the city’s history.”

More recently, federal prosecutors investigated Bill de Blasio, Adams’ predecessor, over his interactions with donors, but brought no charges. And Rudy Giuliani was indicted this year, more than two decades after he was mayor, in a Georgia case focused on efforts to overturn the results of the 2020 presidential election.