Investigators for the Manhattan district attorney questioned the New York City buildings commissioner as part of an illegal gambling investigation and seized his phone on Tuesday morning, according to two people with knowledge of the matter.

The commissioner, Eric Ulrich, 37, a former city councilman from Queens, was approached near his Rockaway Park home by the investigators, who seized the phone pursuant to a search warrant, the people said.

The focus and scope of the investigation by the office of the Manhattan district attorney, Alvin L. Bragg, was not immediately clear, though one of the people said it concerned conduct that predated Mr. Ulrich’s service in Mayor Eric Adams’s administration.

Mr. Ulrich, who served as a special adviser to Mr. Adams before the mayor appointed him to the buildings post in May, has not been accused of any wrongdoing and it is unclear whether the criminal investigation is also focused on other people. A spokeswoman for the Manhattan district attorney’s office declined to comment.

Mr. Ulrich did not immediately respond to a request for comment on Tuesday morning.

Fabien Levy, a spokesman for Mr. Adams, said in a statement that City Hall was unaware of the investigation.

“Our administration has no knowledge of any type of investigation,” Mr. Levy said in a statement. “If an investigation were to be conducted, we would expect any member of this administration to cooperate fully.”

During his three terms on the City Council, Mr. Ulrich served as a member of the Committee on Housing and Buildings. Mr. Ulrich, a Republican, unsuccessfully ran for public advocate in 2019.

The city’s Department of Investigation, which focuses on possible crimes and corruption committed by city employees, has not been involved in the inquiry, apparently because the conduct predates Mr. Ulrich’s appointment and may not have related to his tenure as a councilman, the people said.

But in 2018, Mr. Ulrich wrote a letter on City Council stationery in support of a constituent waiting to be sentenced for conspiring to collect an unlawful gambling debt, The Daily News reported.

“I’d write two letters if I could,” Mr. Ulrich told The News that year when asked about the letter.

In 2021, Mr. Ulrich said on social media that he was battling alcoholism. He said that he discovered he had a problem during the pandemic.

“I regret to say that I developed a drinking problem. What used to be mainly a social activity, and a way to cope with stress, has now become too frequent and self-destructive,” Mr. Ulrich wrote on Facebook. “After talking about this with my family and friends, I have decided to finally quit and get sober.”

Mr. Ulrich also has some personal history of gambling. In 2016, he reported to the city’s Conflicts of Interest Board that he had won between $5,000 and $47,999 gambling, The News reported then.

Mr. Adams has made a habit of hiring executives for his administration with troubled pasts, including heads of departments, advisers and deputy mayors. The mayor has said he is a strong believer in giving people second chances because of his own arrest as a teenager.

“Everybody’s talking about you know, don’t hold a record of a person for the rest of their lives,” Mr. Adams said in an interview earlier this year. “My life was derailed until I was able to get it back on track, and other people should not be derailed.”