Anne Heche was reportedly under the influence of cocaine at the time of her car crash in Los Angeles on Friday (local time).
Law enforcement services reportedly told TMZ the Another World star had cocaine in her system, as well as fentanyl.
Los Angeles Police Department sources told TMZ the department had tested her blood after being admitted to hospital.
It is claimed fentanyl is used as a pain medication in hospitals, but testing and investigation is needed to see if the drug was in her system at the time of the crash.
LAPD officer Jeff Lee told CNN she was now being investigated for felony DUI after the car crashed into a LA home, and then caught fire last week.
Heche's Mini Cooper crashed into a two storey home, before igniting - nearly 60 firefighters were needed to extinguish the blaze.
"Her blood showed signs of impairment and that is why it is now being investigated as a felony traffic collision," Lee said.
"The blood draw results showed a presence of narcotics but additional testing is required to rule out any substances that were administered in the hospital," Officer Annie Hernandez told CNN.
Heche has been in a coma shortly after the collision.
"Anne's condition is dire," TMZ reported. "It has not improved since she was admitted to the hospital .. Anne has been fighting for her life and is in critical condition."
