Four New York Police Department officers had their jobs modified or were transferred this week because of information uncovered during an ongoing joint investigation by the NYPD, FBI and U.S. Justice Department. Police Commissioner William Bratton said in a statement Thursday that Deputy Chief David Colon, Deputy Chief Michael Harrington, Deputy Chief Eric Rodriguez and Deputy Inspector James Grant had been singled out because of the probe of potential violations of NYPD regulations, the city’s conflicts-of-interest rules and federal criminal laws.

“This is not a particularly good day for the department,” the New York Daily News quoted Bratton as telling reporters at a press conference.

Top officials of the NYPD, the largest police force in the U.S., were visited by federal agents about a month ago answer questions over whether they received favors or gifts from two businessmen in return for special treatment, the New York Post reported. The concerns purportedly centered on Jona Rechnitz and Jeremy Reichberg, who reportedly have ties to Mayor Bill de Blasio and who supposedly had cultivated close relationships with the former NYPD chief of department, Philip Banks III, and the city Correction Officers’ Benevolent Association president, Norman Seabrook. Both went to the Caribbean region and Israel largely on the businessmen’s dime, anonymous sources told the Post.

However, both men have denied it, with Seabrook telling the Post, “There is no quid pro quo.”

But the four NYPD officials identified Thursday were also reportedly questioned about cozy relations with the businessmen. Sources said one or more of them had gotten presents from the tycoons such as cash or Super Bowl tickets, according to the Daily News. In return, one or more of them had closed down streets for parties, funerals and weddings, while arranging police protection at the events, the Daily News reported.

The NYPD initiated the investigation in 2013, with the FBI and Justice Department becoming involved the following year. The NYPD’s legal bureau recently reviewed conflict-of-interest rules with senior executives and other employees, Bratton said in his statement.

The investigation is not over. “The public has an expectation of a high degree of trust and integrity its police department,” Bratton said. “We will follow the leads wherever they take us.”