New York City Mayor Eric Adams' phone seized after indictment by ...

New York City Mayor Eric Adams has been indicted by a federal grand jury, sources familiar with the matter told ABC News.

Federal agents appeared Thursday morning at Gracie Mansion and seized the mayor's phone, Alex Spiro, a lawyer for the mayor, told ABC news.

"He has not been arrested and looks forward to his day in court," Spiro said, adding, "They send a dozen agents to pick up a phone when we would have happily turned it in."

In a speech addressed to New Yorkers on Wednesday, Adams vowed to fight what he called the "entirely false" indictment with "every ounce of my strength and my spirit."

"I always knew that If I stood my ground for all of you that I would be a target -- and a target I became," Adams said.

Adams is the city's first sitting mayor to be indicted.

The exact charges remain sealed as of Wednesday night, but the initial investigation expanded from campaign finance to bid-rigging and more, sources said.

A spokesperson for the U.S. Attorney's Office for the Southern District of New York declined to comment.

Adams is not expected to appear in court until next week, sources told ABC News.

Adams, a former police captain who was elected as mayor of NYC less than three years ago, has spent nearly a year under the cloud of federal investigations.

Federal authorities have been investigating the possibility of corruption at City Hall, issuing subpoenas for Adams and members of his inner circle.

Two weeks ago, Adams accepted the resignation of Edward Caban, his handpicked police commissioner, after authorities issued a subpoena for his phones. The mayor's chief counsel, Lisa Zornberg, also stepped down.

This week, New York City Public Schools Chancellor David Banks announced plans to retire at the end of the year. Banks had also turned his phone over to federal authorities.

Banks' younger brothers, Philip Banks, the deputy mayor for public safety, and Terence Banks, also had their phones seized. David Banks' fiancée, Sheena Wright, the first deputy mayor, had her phone seized as well.

Since being elected as New York City's 110th mayor, Adams has been vocal about always following the rules and said he has known of no "misdoings" within his administration.

"If I am charged, I am innocent and I will fight this with every ounce of my strength and spirit," Adams said in a statement Wednesday night.

Brad Lander, New York City's comptroller who is running for mayor next year, released a statement on X following the news of the indictment.

"First and foremost, this is a sad day for New Yorkers. Trust in public institutions — especially City Hall — is essential for our local democracy to function and for our city to flourish. The hardworking people of New York City deserve a city government and leadership they can trust. Right now, they don't have it," Lander said.

Lander called for Adams to step down from his position as mayor.

"The most appropriate path forward is for him to step down so that New York City can get the full focus its leadership demands," Lander said.

If Adams were to heed the calls to resign, the New York City Public Advocate, Jumaane Williams, would become acting mayor. Lander follows Williams in the line of succession.

Earlier Wednesday, Democratic House Rep. Alexandria Ocasio-Cortez of New York called for Adams' resignation, saying, "For the good of the city, he should resign."

"I do not see how Mayor Adams can continue governing New York City," AOC wrote on X. "The flood of resignations and vacancies are threatening gov function. Nonstop investigations will make it impossible to recruit and retain a qualified administration," she added.