Desiigner's Drug Charges Include Methadone, Steroids and OxyContin

Desiigner is in a heap of trouble, because TMZ has learned the drugs cops allegedly found in the SUV in which he was riding included OxyContin, methadone and illegal steroids.

TMZ broke the story, the passengers in the SUV and the driver of a car were involved in a road rage incident Thursday night on the streets of New York. The driver of the car claims Desiigner, who was sitting in the back seat of the SUV, pulled a gun and pointed it at him.

The driver of the car called 911, and cops found the SUV, searched it and found a cache of pills in the console ... so many that all 5 people in the car were charged with felony possession of a controlled substance with the intent to sell.

It's interesting ... methadone is used to treat opiate addiction -- opiates like OxyContin, but methadone can also be abused. As for steroids, it's unclear why they were in the car.

Desiigner was also charged with felony possession of a loaded firearm. Law enforcement sources tell us, cops did not find a gun in the SUV but the rapper was still charged based on the description given by the other driver.

You gotta wonder, how would the other driver know the gun was loaded? He doesn't, but we're told cops routinely file such a charge when they have evidence a gun was in a car. They presume it's loaded.

Law enforcement sources tell us cops have obtained a search warrant to literally take the SUV apart, to see if there's a gun in a hidden compartment.