The Nassau County fire marshal says Adam Rafalowicz was found dead inside his Sutton Place home.
An official cause has yet to be determined. But Fire Marshal Vincent McManus says the victim had a reputation as a careless smoker.
McManus says relatives told him Rafalowicz, who was 86, was a Holocaust survivor and a retired physician.
A neighbor reportedly said that Rafalowicz was a cat lover. No animals were found at the scene.
About 100 firefighters from six volunteer departments battled the blaze, which was called in at about 2:45 a.m.
Nassau police Arson Squad detectives are also investigating.
Copyright 2009 The Associated Press.