03/26/2007 at 04:05 PM EDT
Anna Nicole Smith died of "an accidental overdose with no other criminal element present," Seminole Police Department Chief Charlie Tiger announced at a press conference in Ft. Lauderdale, Fla., Monday.
He said the police conducted a thorough investigation, which included reviewing hundreds of hours of videotapes captured by the hotel security cameras and analyzing the contents of the laptop computer belonging to Smith's companion, Howard K. Stern, and "we found nothing to indicate any foul play."
Broward County medical examiner Dr. Joshua Perper, who earlier had declined to make the autopsy results public until he reviewed the evidence, said that Smith's system contained methadone, anti-anxiety and weight-reducing drugs and, possibly, vitamins, among other substances.
According to the medical examiner's findings, Smith had ingested several medications, including methadone for pain and Valium, but those drugs were at therapeutic levels, said Perper. A bacterial infection from injecting medication in her buttocks and the flu also contributed to her death, said his report.
Also contributing to her death was the sleeping medication chloral hydrate, a sedative used to treat insomnia and alcohol withdrawal, relieve anxiety and ease post-surgery pain, the AP reports.
Rarely prescribed, the drug is known to be fatal if combined with certain other drugs – including the sedative Lorazepam, which the autopsy showed she was taking, said Dr. Chip Walls, a forensic toxicologist for the Miller School of Medicine at the University of Miami.
"It's very toxic if you mix it with any other central nervous system depressant drugs," Walls said. "You could get profound sedation leading up to coma and respiratory arrest."
Smith, a former Playboy Playmate died six weeks ago
, on Feb. 8, in Hollywood, Fla. According to the Associated Press, additional evidence from the Seminole Police Department, which is investigating Smith's death, delayed the autopsy's release.
Tiger said Monday that his department found "no evidence of illegal drugs" at the death scene and had reviewed "hundreds of hours of tapes [and] found nothing unusual."
The day after Smith's death, police said
they had found no evidence that a crime had been committed, and Perper said he'd found no serious injuries in his initial examination.
Perper said at a Feb. 9 press conference that Smith's death could have been due "solely to natural causes ... some medical and chemicals ... or a combination of natural causes and medication."
The much-anticipated disclosure of exactly how the 39-year-old Smith died comes more than three weeks after she was finally buried in the Bahamas
Meanwhile, an inquest into the death of her son, Daniel, in September at age 20 is due to begin Monday
in the Bahamas.