Mark Madoff was found hanged in his Manhattan apartment, WABC television reported. Police would not immediately confirm Madoff's identity, but a New York Police Department spokesman said that "the body of a white 46-year-old male was found by a family member who notified police."
Authorities were responding to the death at a residence that corresponded to the area where Madoff lived.
Mark and his brother Andrew, both close business associates of their father, were under investigation in the massive multi-billion-dollar Ponzi scheme that saw their father sentenced to 150 years behind bars, but they have not faced criminal charges.
Bernard Madoff swindled investors out of tens of billions of dollars in what is believed to be the largest pyramid scheme in history.