02/05/2008 AT 01:00 PM EST
A "big possibility" exists that final autopsy results for Heath Ledger
will be released as early as Tuesday, a spokeswoman for the New York City Medical Examiner's office tells PEOPLE.
The new findings will supplement those of an initial autopsy, whose inconclusive results were announced
on Jan. 23, a day after the 28-year-old actor was found in his Manhattan apartment.
"The autopsy was inconclusive," Medical Examiner spokeswoman Ellen Borakove told PEOPLE on Jan. 23. "We have to do further testing including toxicology and tissue testing. Neither cause of death or manner of death has been concluded."
Michael Baden, a prominent forensic pathologist not involved with the investigation, told PEOPLE the initial inconclusive finding "rules out the natural causes, such as a brain hemorrhage, pneumonia or a cardiac abnormality."
"That leaves drug overdose as the most likely cause of death," Baden said.
Reporting by KATHY EHRICH DOWDFor the complete story of how Heath's partying affected his relationship with Michelle – but never changed her love for him – pick up this week's issue of PEOPLE.