The grisly discovery was made by workers digging with a backhoe due to a sewer problem near one of the buildings at the state psychiatric complex on Clarkson Avenue near East 46th Street, officials said Tuesday.
The remains — which included the half skull and several other bone fragments — were between 10 and 15 feet underground, sources said. They appear to be human, according to NYPD Chief of Detectives Robert Boyce, who spoke about the discovery at a promotions ceremony Tuesday.
"Right now we think this is a disinterment on the burial grounds. We have no leads as far as this is foul play at all. This looks like they’re old bones," he said.
The Medical Examiner will further investigate to determine where they came from, police said. Using forensic anthropology, Boyce said "it might take weeks before we find out more."
Officials at the state's Office of Mental Health, which runs the center, didn't immediately return a request for comment.