Although she had a prescription for the opioid painkiller, the hydrocodone levels in her system surpassed the expected amount roughly four times over, according to the source.
Collier was found dead and naked on Sept. 11 in the Chattahoochee-Oconee National Forest south of Clayton, a 90-minute drive from her home in Athens. Her husband, Steven Collier, reported her missing around 6 p.m. the previous day. She was discovered a few feet downhill from the site of a small fire that burnt up many of her belongings, with soot in her nostrils.
DEBBIE COLLIER CASE: INVESTIGATORS CONSIDER GEORGIA WOMAN'S DEATH MAY NOT BE HOMICIDE, SOURCES SAY
Police found a gas cap nearby, scorched wood, burned personal items and the melted remnant of a plastic fuel jug.
An autopsy report obtained Monday by the New York Post reveals that the "charring" to her stomach was not a full description of the burns she'd suffered. She had "second- and third-degree burns involving 80% of the total body surface area," leaving her with "charred leathery skin."
"Autopsy examination revealed thermal injuries of the external body surface and of the traceal mucosa (windpipe), no deposited soot in the airway, and no significant elevation of blood carboxyhemoglobin," the Post quoted in an excerpt of the report.
SLAIN GEORGIA WOMAN DEBBIE COLLIER REMEMBERED AS BELOVED MATRIARCH ‘FILLED WITH JOY AND BEAUTY’
She had "no other significant injuries" and the authors theorized the burns may have come from a "sudden, intense ‘flash’ fire."
In support of investigators' suicide declaration, the autopsy reportedly only mentioned, "Investigation by law enforcement revealed circumstances consistent with a self-intentioned act and that she was alone at the time of the incident."
Law enforcement sources told Fox News Digital the conclusion was drawn from the toxicology report, depression, and an unsent text message to her son reading "I love you."
Prior to her disappearance, Collier sent her daughter a Venmo payment of almost $2,400 along with the message: "They are not going to let me go love you there is a key to the house in the blue flowerpot by the door."
Collier was last seen alive at a Family Dollar store on Sept. 10, purchasing several items that were found burned near her remains. She also stopped by a Chick-fil-A restaurant beforehand.
Law enforcement sources previously told Fox News Digital that investigators had no evidence linking several key people close to Collier, including her husband, daughter and daughter's boyfriend, to locations anywhere near the crime scene between her disappearance on Sept. 10 and the discovery of her remains the following day.