Andrew Koppel was declared dead around 1:30 a.m. Monday in the apartment in the Washington Heights neighborhood, Detective John Sweeney said.
Ellen Borakove, a spokeswoman for the city medical examiner, said an autopsy was performed Monday but results were pending further study, including toxicology and tissue testing.
Additional tests were needed to determine the manner and cause of death, Borakove said. They will take a few weeks to complete, she said.
Koppel had been drinking for hours with a man he met at a bar, the New York Post reported Tuesday.
"He had a straw hat on, and I had one on, and he said, 'Nice hat, man,'" his drinking partner, Russell Wimberly, told the newspaper. "We got to talking, and he started buying me drinks."
Wimberly said that Koppel drank whiskey, and that neither man had anything to eat all day.
Koppel was appointed attorney for the city Housing Authority's civil litigation division in 2001, a post he resigned in 2008, the agency said Tuesday.
Ted Koppel was the longtime anchor of the ABC News show "Nightline." Andrew Koppel, of Queens, was one of his four children. A call to the elder Koppel's publicist was not immediately returned Tuesday.
Andrew Koppel was convicted of misdemeanor assault in 1994 for striking a U.S. Senate aide during an argument at a Capitol Hill automated teller machine. At the time, he was a student at Georgetown Law School.
Wimberly said that after drinking, he and Koppel eventually wound up at the apartment, which belonged to Wimberly's friend. He and the friend, Belinda Caban, told Koppel to sleep it off and later found that he had gotten sick and appeared not to be breathing, the Post said. The two said they called 911.