The city's Medical Examiner says the swimsuit designer found dead in a swanky Manhattan Hotel earlier this month was strangled and drowned.
The ME's office ruled the death of Sylvie Cachay, 33, a homicide.
Officials believe Cachay was held under water while being strangled.
Her body was found half clothed, submerged in a bath tub on December 9.
Staffers at the SoHo House hotel in the Meatpacking District found her body after looking into why water was leaking from the ceiling below her room.
Her ex-boyfriend, Nicholas Brooks, 24, was arrested in connection with her death.
The exact charges against him are sealed until his arraignment on January 4.