Mayor Bill de Blasio and NYPD Commissioner William Bratton were tight lipped Tuesday about a federal probe into possible corrupt payments given to high ranked NYPD officers by some businessmen in exchange for favors.

De Blasio refused to comment while Bratton, who usually talks openly about corruption investigations by his internal affairs unit, acknowledged the inquiry but said there was little he could say.

“Those of you that cover us routinely understand that on these investigations we’re not able to comment on them and that’s an agreement with the [Federal Bureau of Investigation],” Bratton said at an appearance in Brooklyn Tuesday.

De Blasio cut off questions related to the investigation during a news conference on homelessness, saying, “This topic, that’s all we’re doing today.”

But Bratton did acknowledge that one detective, identified in reports as Michael Milici, had been placed on modified assignment “for the good of the department.” Modified status means that an officer has surrendered his gun and badge and is essentially doing desk duty.

“It’s the nature of the business that always results unfortunately in investigations,” Bratton said. “We’ll just have to see where the investigation goes and it’s something that as you would expect that we will participate in and cooperate fully with.”

Patrick V. Parrotta , Milici’s attorney, didn’t return a telephone call for comment.

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Law enforcement sources said that the FBI and Manhattan U.S. Attorney Preet Bharara were investigating allegations of corruption in the police department involving businessmen.

Sources familiar with some aspects of the probe who didn’t want to be named said that the federal inquiry is looking into relationships between businessmen Jona Rechnitz and Jeremy Reichberg and certain current members of the NYPD. Rechnitz and Reichberg are well known police buffs who are prominent in Jewish philanthropy. Both have been major de Blasio supporters, with Reichberg having hosted a dinner at his Borough Park home for the mayor in May 2014, according to news reports.

The sources indicated that former NYPD chief of department Phil Banks and correction union president Norman Seabrook have socialized and traveled with Rechnitz and Reichberg while Banks was still on the job. City conflict of interest rules prohibit city employees, who left the department in late 2014, from taking anything worth more than $50 from a person they knew or should have known was doing or seeking to do business with the city. Labor unions are governed by different rules that generally bar accepting anything of value from management or in return for doing business.

One person who was questioned by Southern District prosecutors, FBI agents and forensic accountants working for the Southern District several months ago said law enforcement officials were interested in the relationship between Banks and Seabrook, who paid for their overseas travels, as well as the correction’s union’s deposit of millions of dollars of its funds in a hedge fund. The person, who did not wish to be identified, did not name the hedge fund.

A spokesman for the Correction Officers Benevolent Association declined to comment Tuesday. Banks also declined to comment. Rechnitz and Reichberg didn’t return telephone messages for comment.

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With Matthew Chayes