Brandon Clarke had an unknown white powder, Narcan, syringes and a slew of medications inside his home when he was found dead ... TMZ has learned.

According to the Los Angeles County Medical Examiner's report, investigators found vape devices, cannabis products, prescription medications, injectable peptides, syringes and a box of Narcan inside Clarke's bedroom and attached bathroom.

Investigators also found a plate containing an unknown white powdery substance on the kitchen island ... along with a hotel key card.

As TMZ previously reported ... Clarke was found unresponsive in bed at his Los Angeles-area home in May, and the medical examiner later ruled his death an accident caused by the effects of heroin and cocaine, with multiple prescription medications contributing.

The report says there were no apparent signs of foul play or fatal injuries at the scene.

Story developing ...