Cory Monteith did NOT die from a new strain of deadly heroin that has been going around the Vancouver area -- this according to the coroner.
A police dept. 40 miles from Vancouver had issued a release warning a "toxic' mixture of heroin and fentanyl has caused a spike in heroin ODs.
The coroner who did the autopsy on Cory tells TMZ ... NO FENTANYL was found in Cory's system.
We're hearing the likely scenario is that Cory had not used heroin since entering rehab in April, and he may have gone back to the same dose he had learned to tolerate when he was using, but because his body was clean it couldn't handle the shock.
Cory Monteith's body was cremated Tuesday in Vancouver following a private viewing with his family and girlfriend Lea Michele, TMZ has learned -- but Cory's father wasn't invited ... and he's heartbroken.
Cory's dad Joe Monteith -- who is divorced from Cory's mom Ann -- tells TMZ ... he was informed of the cremation after the fact, adding he's "totally devastated" he didn't get a chance to see Cory's body.
We're told Cory's body was released yesterday to his mom, and she decided to hold a viewing at the hospital with Lea and Cory's brother Shaun. Following the viewing, we're told Cory's mom decided to have him cremated.
Cory's dad tells us, "I always loved both my sons and am going to miss Cory very very much. I'm saddened at the fact that I couldn't have been there to see my son before he was cremated."
As for Cory's alleged heroin use ... his dad says he's "shocked."
The cast of "Glee" -- along with several producers -- knew Cory Monteith was battling a heroin addiction earlier this year and were the catalyst in his decision to go back to rehab, TMZ has learned.
Sources connected to the production tell us ... it was no secret Monteith was off his game back in March -- and it became clear he was relapsing, specifically with heroin.
We're told the cast and the producers became very concerned ... and knew they had to address the issue with Cory.
Sources say ... the group sat down with Cory and had an "open conversation" with the actor -- stressing how much they cared about him and wanted him to get help.
One source tells us Cory was very receptive -- "It wasn't met with resistance ... He was always so grateful and aware of how fortunate he was."
"The decision was to best help our friend. The needs of the show fell second to his well-being."
Cory voluntarily checked into rehab at the end of March for a 30 day stint ... but despite his efforts, he couldn't defeat his demons, and last week, he died from a lethal mixture of heroin and alcohol.
3:10 PM PT -- Officials are currently addressing the media about the death investigation.
Cops wouldn't delve into specifics when asked if they found drugs in Cory's hotel room, but they certainly insinuated it ... saying, "There was evidence in the room that was consistant of a drug overdose."
Cory Monteith died from a lethal combination of heroin and alcohol ... this according to Canadian authorities.
The British Columbia Coroners Service says an autopsy and toxicological analysis show that the 31-year-old "Glee" star died from a "mixed drug toxicity, involving heroin and alcohol."
Monteith's body was discovered by staffers at the Fairmont Pacific Rim hotel in Vancouver, Canada on July 13.
Monteith had struggled with addiction for years and had been to rehab earlier this year.
Monteith had said he began struggling with drugs and alcohol as a young teenager.
Cory Monteith was leading a double life -- a hard-working, "Glee" star in L.A. struggling to stay clean ... a hard-partying substance abuser in Vancouver.
CORY'S L.A. LIFE
Our sources say Cory's GF Lea Michele and his "Glee" cast knew his struggles all too well and spent a lot of time keeping him clean and sober. We're told Cory never showed up on the set under the influence of anything and most of the time abstained from drugs and alcohol.
The pic above shows the last trip Cory and Lea took together -- it was taken on June 18th in Fire Island, where they visited a friend on a movie set. We're told Cory was sober the entire time.
There were, however, lapses, which is why he checked into rehab in April.
CORY'S LIFE IN VANCOUVER
Our sources say Cory's resolve to stay clean dissipated whenever he returned to his native Canada. That's where he became a drug addict with a serious drinking problem.
Corey went back to Vancouver many times, and hung out with many of the friends who helped fuel his addiction. We're told alcohol and drugs were always involved.
Our sources say Cory's family was aware he reverted back whenever he went North of the border, and they tried in vain to help. We're told as family members became alarmed recently and began making a full-court press ... Cory became distant.
Somehow, Cory was able to compartmentalize his life into a tragic tale of 2 cities ... and the city where he slipped became the city where he died.
These are some of the last photos ever taken of Cory Monteith -- snapped just days before he was found dead in a hotel room -- while the "Glee" Star was hanging with friends and drinking alcohol.
Sources tell TMZ ... the pics were taken on July 6th, the same day Cory checked-in to the Fairmont Pacific Rim hotel in Vancouver ... where he was found dead one week later.
In the pics, Cory and a few buds are seen hanging out at The Shop -- a local coffee house and clothing store for people who love motorcycles.
We spoke to the owner, who tells us, Cory came in ... was extremely friendly and really interested in choppers ... even sitting on the owner's bike.
We're told he and his friends chilled for awhile -- laughing and drinking beers. One source on-site said Cory knocked back 3 cold ones over the course of a few hours -- despite his recent stint in rehab -- but didn't seem out of control or wasted. He was perfectly nice.
Cory's not physically seen drinking in the pics ... but the Lea Michele doppelganger he's standing next to -- who we're told is just a friend -- is seen clutching two beer cans. Possibly because cameras were around ... and Cory has been open about his substance abuse issues.
As TMZ previously reported ... Fairmont hotel staff found Cory dead in his hotel room Saturday, after spending Friday night out with friends. He was 31.
Now here's Cory's best moment in "Glee" history ... R.I.P.
Cory Monteith -- who famously played Finn Hudson on the TV show "Glee" -- died early Saturday morning in Vancouver ... he was 31 years old.
According to police in Vancouver the actor was found dead in his hotel room on the 21st floor of the Fairmont Pacific Rim Hotel around noon ... when staffers went to check on him after the actor missed his check-out time.
In a press conference, officials said the actor was "clearly deceased" -- and had been so for several hours -- when police arrived on the scene.
Cops say Cory checked-in to the Fairmont on July 6th and was scheduled to leave July 13th. It is unclear why he was in Vancouver, but cops did mention he's from Canada and visits often.
The night before his death, Cory was seen in his room hanging with friends, before hitting the town ... but came back early Saturday morning ... alone.
Cops say "it was not immediately apparent" what caused his death, but no foul play is suspected. An autopsy is scheduled for Monday.
A rep for the actor says they are "in shock and mourning this tragic loss."
As TMZ previously reported, Monteith voluntarily checked himself into a treatment center back in April, admitting he had substance abuse issues. It was his second time in treatment.
Prior to that, Cory had been open about his problems with drugs. Back in 2011 he told Parade Magazine, his family and friends were so afraid he "could die" they staged an intervention. He was 19 at the time.
He explained that his drug use consisted of "Anything and everything, as much as possible." Adding, "I had a serious problem."
"Glee" co-star Matthew Morrison took time out of a performance Sunday to pay tribute to Cory Monteith ... in the most "Glee" way possible ... belting out a Broadway show tune.
Matthew -- who plays Finn Hudson's mentor / teacher on the show -- played a gig at 54 Below in NYC. Prior to the set, Matthew addressed the tragedy of Cory's sudden death and referred to the actor as a brother ... as reported by the NY Times.
Matthew then changed his opening number -- and dedicated the song to Cory.
He chose "What I Did For Love" -- a show tune from "A Chorus Line" -- which was also featured on "Glee" Season 2 and sung by Lea Michele.