Even as 200 mourners lit candles and jammed the incense-rich chapel of the Synodal Cathedral of the Mother of God of the Sign on East 93rd Street, a private investigator was videotaping the teary-eyed crowd - looking for shady characters who didn't belong.

Stephen P. Davis was hired by the family to investigate what happened to Svetlana, a married mother of two who disappeared March 3, while walking her dad's dog.

"We're also working with the FBI and the NYPD, but they have no clue as to what really happened," said Steve Klein, a family friend.

Aronov's body - bruised on and below the knees - surfaced in the East River last week, on the Queens side of the 59th Street Bridge.

A Cartier watch and a gold ring she was wearing was still on her body.

She was identified by dental records.

A witness told cops he saw Svetlana and the dog, which has not been found, get into a taxi, but no cabby has come forward to say he had her as a passenger. There is no witness who saw her go into the water.

The medical examiner's office is still probing the circumstances of her drowning - which could have been the result of a suicide, accident or murder.

But at the funeral yesterday, friends and family said they'd ruled out two of the options.

"I don't believe she committed suicide," said Svetlana's friend, Nataliya Dyakovskaya. "Maybe somebody was threatening her. As a Russian, I always suspect foul play."

Klein, too, ruled out suicide.

"And it's hard to understand how this could have been an accident," he added. "The dog, the cell phone, her keys and her coat are still missing. We always believed there was foul play."

Cops said Aronov sought psychiatric treatment for depression in 1995, but they have not been able to access her medical records because of doctor-patient confidentiality.

Both Svetlana and her doctor husband, Alexander Aronov, had affairs and sometimes lived apart in different countries for years at a time during their 25-year marriage.

He attended yesterday's service with his two daughters, his father, stepmother and Svetlana's parents. Friends and family said yesterday they do not believe he was involved in his wife's death.

Svetlana legally fled Russia during the Communist era with Alexander, a Russian Jew who claimed religious persecution.

Other mourners who crammed the Russian Orthodox Church on the Upper East Side represented all aspects of her life - childhood friends from St. Petersburg, йmigrй friends from Toronto, where the family lived before moving to New York in 1989, her colleagues in the rare Russian book business and her peers from Alexander's two medical offices, where she kept the books.

After the service, the mourners traveled to Long Island, where Svetlana was buried in Southampton Cemetery near the family's weekend home.