A 54-year-old man died in police custody after falling ill in Brooklyn, cops said Sunday.

Reginald Newkirk became sickly on Saturday at the NYPD’s 67 Precinct station house around 2:12 p.m. on Snyder and Nostrand Aves. in Flatbush.

EMS rushed Newkirk to Kings county hospital, where he died on Sunday.

The cause of Newkirk’s death was still unknown.

The NYPD’s Force Investigation Division is launching an investigation into the incident.

Newkirk lived in Brooklyn, cops said.