A former top NYPD official died of a 9/11-related illness on Thursday morning, police said.

William Allee, who served as the department’s chief of detectives from 1997 to 2003, died around 6 a.m. at Memorial Sloan Kettering Cancer Center. He was 76.

Allee had apparently suffered from leukemia, officials said.

He joined the NYPD in 1963 and was promoted to detective four years later. Before becoming chief of detectives, he served as commanding officer of the 7th Precinct on the Lower East Side, as well as the Midtown North precinct and headed detective operations in Staten Island, where he lived.

He retired Feb. 15, 2003, the 40th anniversary of his first day on the force.