A man was found dead in a Brooklyn Heights building Saturday and authorities are probing the circumstances surrounding his demise, police said.

At around 1:10 p.m., police responded to a 911 call of an unconscious man at 57 Joralemon St., and discovered the victim, “unconscious and unresponsive,” on the third-floor steps inside of the building, cops said.

Responding EMS personnel pronounced the man, 36, dead at the scene.

“He was not a resident of the building. It’s unknown what he was doing there,” an NYPD spokesman said, adding no drug paraphernalia was found near the deceased. The Medical Examiner will determine the cause of death.

The name of the deceased is being withheld pending family notification, authorities said.