Edward A. Caban, the New York City police commissioner, announced his resignation in an email to the Police Department on Thursday, eight days after federal agents seized his phone as part of a criminal investigation.

Commissioner Caban, 57, had been under pressure to resign from Mayor Eric Adams’s administration, which had asked him to step aside on Monday, according to two people with knowledge of the matter.

City Hall has been buffeted by four federal investigations, which have resulted in searches and phone seizures targeting high-ranking city officials, including Commissioner Caban. The U.S. attorney’s office for the Southern District of New York is overseeing the investigation involving Mr. Caban, as well as two of the other inquiries focusing on officials in the Adams administration.

Commissioner Caban said in the email that he was resigning because the “news around recent developments” had made it impossible to focus fully on “the department and people I love and have dedicated over 30 years of service to.”

“The N.Y.P.D. deserves someone who can solely focus on protecting and serving New York City, which is why — for the good of this city and this department — I have made the difficult decision to resign,” Mr. Caban wrote.

A statement from Commissioner Caban’s lawyers, Russell Capone and Rebekah Donaleski at the firm Cooley LLP, is expected to say that federal prosecutors have told them that he is not a target of the investigation, and that he intends to fully cooperate with the government.

The two lawyers are former chiefs of the corruption unit at the U.S. attorney’s office for the Southern District.

Prosecutors from that office, along with agents from the Internal Revenue Service, are examining a nightclub security business owned by the commissioner’s twin brother, James Caban, a former police officer who was fired from the department in 2001. James Caban also had his phone seized last week, according to one of the people.

None of the officials involved in the investigations have been charged with a crime, but the seizures have upended the administration of Mr. Adams and raised questions about his ability to run New York City.

The departure of Commissioner Caban is a remarkable conclusion to a decades-long career that began in the South Bronx, where he started as a patrol officer in 1991, and culminated with his appointment as the first Latino commissioner in July 2023.

Mr. Adams, who appointed him, hailed the decision as “historic” at the time. But in the days since the commissioner’s phone was seized, speculation grew over when he would announce his resignation.

This is a developing story and will be updated.