A construction worker discovered human remains while repairing a sewer system near the campus of an East Flatbush psychiatric hospital Monday afternoon, according to the NYPD.

The grisly discovery was made at 781 Clarkson Avenue at the corner of East 48th Street just before 1:30 p.m. on Monday, a spokesman for the department said. The human remains were sent to the office of the medical examiner to confirm cause of death.

The Daily News reports that the remains included a skull and arm and leg bones thirteen feet below the surface. It was not immediately clear how long the bones had been there, or when the person died.

The Kingsboro Psychiatric Center is a state-run facility.