Anna Nicole Smith's 20-year-old son died from a lethal combination of methadone and two antidepressant drugs, a pathologist who conducted a private autopsy on the body said Wednesday.

Toxicology tests showed Daniel Smith had methadone, Zoloft and Lexapro in his system when he died Sept. 10 in a hospital room in the Bahamas where his former Playboy playmate mother was recuperating from giving birth to a daughter, according to Cyril Wecht.

"The fact that we have these drugs and the levels of the drugs overwhelmingly and most logically point to this being a tragic, accidental, drug-related death," Wecht told The Associated Press from his home in the Pittsburgh, Pennsylvania area.

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Wecht said Smith apparently died from a "classical" combination of the drugs which had a lethal "cumulative effect on the central nervous system."

"Coroners working around the country, we see this in people taking two or three drugs or more," he said.

Smith had been reported to be suffering from depression in the weeks before he went to the Bahamas to visit his reality TV star mom and his newborn half-sister. Zoloft and Lexapro are antidepressants commonly prescribed for patients with anxiety and panic disorders.

Methadone, a pain-reliever, is also commonly used by people recovering from drug addictions.

"It is used for people who have been on heroin or morphine," Wecht said. "I have made those inquiries. I can only say to you no one has suggested anything having to do with drug addiction in this boy."

Wecht said he would share his results Thursday with the pathologist who conducted the official autopsy in the Bahamas, but did not know whether they would issue a joint report on the death.

In Nassau, Chief Magistrate Roger Gomez said he has not yet received official toxicology results, which will determine whether or not a jury inquest into the death is necessary.

Smith's body remained at a Bahamas funeral home hired by the family Wednesday.

Howard K. Stern, a lawyer for Anna Nicole Smith who was in the hospital room when Daniel died, told CNN's "Larry King Live" on Tuesday that he is the father of the 3-week-old baby girl, Dannie Lynn Hope.

But photographer Larry Birkhead, a former boyfriend of Anna Nicole Smith, told Us Weekly magazine that he's the father and is seeking a DNA test to prove it.

Stern said he plans to marry Smith "at some point."

"Right now we have to somehow get through what we're going through," said Stern, adding: "And I'll tell you, our baby is the one ray of hope."

Daniel Smith, who appeared several times on the E! reality series "The Anna Nicole Show," was the son of Anna Nicole and Bill Smith, who married in 1985 and divorced two years later.

Anna Nicole married Texas oil tycoon J. Howard Marshall II in 1994, when she was 26 and he was 89. He died the following year and she has since been involved in legal disputes over the estate.

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