Mayor Eric Adams was riding high in the fall of 2022 when Winnie Greco, one of his best fund-raisers and a top adviser, led him into a glittering ballroom in Flushing, Queens, the heart of the Chinese diaspora in New York City.

She and Mr. Adams took their seats at the head table of the event, an anniversary celebration for a nonprofit with close ties to the Chinese Communist Party, and watched as the host, Jimmy Lu, rose to address the crowd.

Mr. Lu bragged in Mandarin about opening a Chinese government police station in the offices of the nonprofit in Lower Manhattan — an illegal outpost that federal authorities would later say was used in a sprawling transnational repression scheme. The police station, Mr. Lu said, his remarks being translated into English, would help “implement the motherland government’s policy of benefiting the overseas Chinese.”

Then it was Mr. Adams’s turn. Taking the same stage, he began to praise Mr. Lu’s group. “This is such an important organization,” the mayor said, “to empower our Chinese American community.”

Later, after Mr. Lu’s brother Harry was arrested in connection with the police station and charged with acting as an unregistered agent of the Chinese government, Mr. Adams’s aides would not respond to questions from reporters about whether he heard Mr. Lu talking about the police station, or knew of its alleged role in spying on Chinese dissidents.

The episode underscores Ms. Greco’s close and abiding ties to the People’s Republic of China, and the perils that connection has posed for Mr. Adams. And while the federal corruption charges Mr. Adams now faces after being indicted last month are not centered on his ties to China, prosecutors have recently demanded information from him and his staff about that country and others. They have also indicated that more charges are likely — both for Mr. Adams and others in his orbit.