“We will follow the leads wherever they take us,” he said.

While roughly 20 police officials have been questioned in recent weeks as part of the federal inquiry, three people briefed on the matter have said it is focused more closely on the conduct of two businessmen with ties to Mayor Bill de Blasio and how they may have sought to wield their influence.

Agents with the Federal Bureau of Investigation who are assigned to a squad that mostly investigates political corruption are continuing to gather evidence, and the federal authorities have not ruled out charges against any of the officers, according to the people briefed on the inquiry, who spoke on the condition of anonymity because they were not allowed to discuss the matter.

A federal grand jury has begun hearing evidence in the matter, and one person briefed on the case said several of the police officials, accompanied by their lawyers, had discussed the possibility of cooperating with prosecutors.

The inquiry grew out of two separate investigations that were quickly merged, one of which the Police Department’s Internal Affairs Bureau started in December 2013 and the other initiated by prosecutors from the United States attorney’s office in Manhattan. Police officials said the two inquiries were combined in early 2014.

The original federal inquiry was focused on Philip Banks III, the police force’s chief of department at the time, and Norman Seabrook, the head of the union that represents New York City correction officers. Investigators were examining the men’s financial dealings and whether Mr. Seabrook had enriched himself during his two decades running the union, people briefed on the matter said.