She passed away earlier this week and an autopsy was performed on Saturday, but Lisa Robin Kelly's cause of death is still unknown.

According to a coroner's office spokeswoman, it will take two months for toxicology results to come back from the lab.

On Wednesday, the "That '70s Show" star died in her sleep at a treatment facility to help treat her various addictions.

Though she's battled the demons for years, her death was a shock, as her agent Craig Wyckoff told PEOPLE, "I spoke to her on Monday, and she was hopeful and confident, looking forward to putting this part of her life behind her."