Andy Irons did die from heart disease -- as his family announced yesterday -- but methadone and cocaine also played a part in the surfing champion's death ... according to the official autopsy report.

According to the
Tarrant County Medical Examiner's report, "The primary and underlying cause of death is ischemic heart disease due to coronary artery pathology."
The report lists the manner of death as, "Natural."
However, the report continues, "Drugs ... particularly, methadone and cocaine, are other significant conditions contributing to death but not resulting in the underlying cause."
The family of surfing legend
Andy Irons is adamant the former world champ died as a result of complications from heart disease -- and nothing else -- however, the official autopsy report shows drugs were a factor.

Seven months after Irons died in a Dallas hotel room, Andy's family released a statement today explaining Irons died from a heart attack caused by the hardening of his coronary arteries. The family says they spoke with a prominent forensic pathologist who explained Irons had a genetic predisposition to early development of heart disease ... which was SOLELY responsible for the heart attack.
However, the toxicology report and the autopsy from the Tarrant County Medical Examiner note a second cause of death -- "acute mixed drug ingestion."
TMZ has just obtained a copy of the police report in the
Andy Irons death investigation -- in which cops say they found various prescription drugs in the surfer's hotel room ... but there's no mention of methadone.

The report says when police entered the surfer's hotel room at the Dallas/Fort Worth International Airport in Texas they discovered Irons' body on the bed "laying on his back with the sheet pulled up to his neck. The bed covers and pillows were neatly set and nothing appeared out of the ordinary."
According to the report, police found bottles of alprazolam (the generic version of Xanax) and zolpidem (the generic version of Ambien) on the tables near the bed.
The Star Advertiser claimed in a previous report that investigators discovered methadone inside a zolpidem bottle -- but there was no mention of methadone in the police report.
A crime scene investigation was conducted -- and a report on the investigator's findings are forthcoming.
Kelly Slater -- one of
Andy Irons' greatest surf rivals -- is opening up about the sudden passing of his friend ... saying, "I'm lucky to have known him and had the times we had together."

In a statement, released today, Slater says, "I feel blessed that we worked through the differences we had and I was able to learn what I'm made of because of Andy."
Slater continues ... "He was the most intense competitor I've ever known and one of the most
sensitive people. He had so much life left in him and it hurts to think
about."
Check out the full statement after the jump ...
Dozens of pro surfers gathered in
Puerto Rico this morning to honor their fallen brother, surf legend
Andy Irons.

According to the
Association of Surfing Professionals, Irons' friends Roy Powers and Dusty Payne led the paddle out -- followed by fellow ASP World Tour surfers, friends, industry representatives
and fans who carried bouquets of flowers.
As we previously reported, Irons passed away yesterday in Dallas -- after traveling from a surfing event in Puerto Rico.
We took your questions today on everything -- including
Mel Gibson's deposition,
Cirque du Soleil's new
Michael Jackson show, and
Levi Johnston unloading on
Sarah Palin.
Plus: Harvey's favorite fish!
Surf legend
Andy Irons reportedly had "numerous" medications in his Dallas, TX hotel room in the wake of his death -- including methadone.

According to Hawaii's
Star Advertiser newspaper -- the Tarrant County Medical Examiner's Office claims the methadone was found inside a container of a prescription drug called zolpidem (sleep aid) ... which was on Andy's nightstand inside the hotel room.
An investigator with the Tarrant County M.E. tells TMZ they did not release any information about methadone to the Star Advertiser -- but we spoke to the reporter, who tells us someone at the M.E.'s office volunteered the info to him when he called. The reporter did not specify who he spoke to at the M.E.'s office.
As we previously reported, the 32-year-old surfing champ -- considered by many to be one of the best in the world -- was found dead yesterday at the Grand Hyatt Hotel in Dallas.
Irons' family released a statement suggesting he may have been suffering from dengue fever ... though methadone is not typically used to treat that illness.
Three-time surfing world champion
Andy Irons died this morning at a hotel in Dallas ... TMZ has learned.

The 32-year-old was found by a hotel employee around 10:00 this morning.
According to reports, Irons had planned to travel back to his home in Hawaii -- but fell ill and that's why he booked his room in Dallas.
The local medical examiner tells us an official cause of death has not been determined.
The Irons family has released a statement saying, "[Andy] had reportedly been battling with
dengue fever, a viral disease."