A Quebec coroner's report into Montreal boxer Arturo Gatti's 2009 death, obtained by CBC News, questions the quality of the Brazilian investigation but ultimately is unable to determine whether the former world champion killed himself or was slain.

The coroner, Jean Brochu, agrees with prior conclusions that Gatti died a violent death from asphyxia by neck constriction.

"The conclusion of the Montreal pathologists to the effect that there is no clear evidence of foul play in Mr. Gatti's death means I cannot dismiss the formal conclusions reached by the authorities of the country where it occurred."

Brochu questions the quality of the Brazilian police investigation, "especially in regard to the examination of the scene where the death occurred," he writes, which "does not meet the standards we have grown accustomed to here."

"The methods used by the Brazilian investigators in examining the scene of Arturo Gatti's death can raise doubts, and so the [coroner] believes that the circumstances of death cannot be determined with certainty."

Gatti's body was discovered on July 12, 2009, in the Brazil hotel room where he was vacationing with his wife, Amanda Rodrigues, and their infant son, Arturo Jr.

Brazilian authorities originally declared it homicide and arrested Rodrigues in her husband's death. She was held in custody for nearly three weeks before an autopsy determined Gatti had committed suicide by hanging himself with his wife's purse strap.

U.S. private investigators hired by Gatti's friends, however, concluded in a 300-page report that Gatti had been slain. The private investigators concluded that Gatti had been hit from behind and strangled.

However, Brochu's report cast doubts on the findings of the private investigators, saying they had "obvious shortcomings".

"The failure of American detectives to explain the obvious presence of post-mortem lividity on Arturo Gatti's body (indicating that the body had been suspended for some time before ending up on the floor) raises doubts about their assessment on the cause of Mr. Gatti's death."

The report from the Quebec coroner also noted that Gatti had carisoprodol, a muscle relaxant in his system, along with alcohol. While Brochu said toxicology tests don't allow for any definitive conclusions, an expert toxicologist from Quebec retained by the coroner said the drug can produce withdrawal symptoms, such as anxiety, confusion and psychosis.

Toxicologist Dr. Martin Laliberté stated: "Although carisoprodol is clearly not directly responsible for the death, I believe that its presence can give rise to some pertinent questions: sedative effect at the time of death? Overdose? Withdrawal syndrome? The answer isn't immediately apparent."