NEW YORK -- The autopsy of a Manhattan rare-book dealer has come up inconclusive, deepening the mystery surrounding her two-month disappearance and death.

The medical examiner's office said Thursday that its investigators could not determine whether Svetlana Aronov died in an accident, a homicide or a suicide.

The autopsy last month revealed the cause of Aronov's death as drowning after a ferry captain found her body on the Queens side of the East River.

Progress in the case largely stopped there, however, and police detectives have followed a dwindling number of leads. They have tried to match small bruises on Aronov's shins to an East River guardrail and attempted to fix the time of her death by researching her Cartier watch's ability to withstand submersion.

Some detectives now believe Aronov committed suicide, police said. One police official said Thursday, however, that much of the physical evidence, such as bruises on Aronov's face, did not point conclusively to any single theory.

Aronov's family members do not believe Aronov committed suicide, but they remain perplexed about the potential motive for a homicide and the possibility of an accidental drowning, according to their attorney.

The lingering question mark has deepened the family's sorrow, lawyer Ed Hayes said Thursday.

Aronov, 44, disappeared on March 3 while walking her cocker spaniel, Bim, on the Upper East Side. She was reported missing after she failed to pick up her father from the airport.

A parking lot attendant told authorities that he saw Aronov get into a taxi around the time police believe she disappeared. The attendant said she appeared to know the driver.

Aronov's husband, Alexander Aronov, a doctor, said he found that account unlikely since his family did not know any taxi drivers.

The couple, both natives of St. Petersburg, Russia, have two daughters.