Long Island dermatologist Kiersten Cerveny, who was found unconscious and unresponsive in the lobby of a Chelsea apartment building on October 4, died from acute cocaine and alcohol intoxication, the city medical examiner said late Monday.

Cerveny, 38 and mother of three children, had partied hard the previous evening, police said, and went with a friend, HBO producer Marc Johnson, to an apartment at 223 W. 16th St. where investigators believe she may have taken more drugs.

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Cerveny's death was considered accidental, said the medical examiner's office in a statement.

A former beauty queen, Cerveny had offices in Manhasset. Earlier in the investigation, police sources said they didn't believe there was any criminality involved in her death.

Law enforcement sources also said initial tests at the time of the autopsy indicated Cerveny had used cocaine but final results were pending toxicological tests.