Homicide chief Lt. Jack Fitzpatrick said Monday investigators believe the fire from the cooking oil came from another apartment in the two-story structure on Little East Neck Road, which also houses the West Babylon Lions Club and the China King restaurant on its first floor.
Firefighters found the body of the woman Sunday at about 6:30 p.m. Fitzpatrick said he doubted the identity of the woman would be released on Monday.
Suffolk County's Arson Squad also is investigating, Fitzpatrick said.
North Babylon Fire Chief Thomas Jordan said the body was discovered after firefighters worked about two hours to contain the blaze.
Jordan said the West Babylon, Babylon, East Farmingdale and Wyandanch fire departments also responded to the scene.
One resident was taken to Stony Brook University Hospital and another was taken to Good Samaritan Hospital Medical Center, Jordan said. Their conditions were not known Monday. Suffolk police Sgt. Jim Messina said the fire is not believed to have started at the restaurant.
Residents who live in the building said the blaze could mostly be seen burning on the building's second floor.
"I just saw thick black smoke coming through my walls and when I opened my door, it was a wall of smoke," said Eddie Hernandez, 28, who was able to flee the building with his girlfriend.
With Gary Dymski