Racial stereotypes may be playing a role in the US opioid overdose epidemic, according to a leading expert on opioid addiction.

The rate of white Americans dying annually from drug overdoses has roughly doubled from 2002 to 2014, while the rate of black Americans and Hispanics who die from drug overdoses has remained almost unchanged over that same time frame, according to recently released data from the CDC.

Dr. Andrew Kolodny, the chief medical officer for The Phoenix House and a leading expert on opioid addiction, told Business Insider these trends might have a direct connection to some doctors allowing racist stereotypes to influence the way they prescribe opioid pain killers.

"What's happening is we're overexposing whites to prescription opioids," he said. "Doctors prescribe narcotics more cautiously to black patients. It appeared the doctor may be more worried about addiction or diversion of the pills onto the black market if the patient was black and if the patient is white, they're overprescribing."

The armed occupiers of the Malheur National Wildlife Refuge continue to use government equipment inside the complex.

One militant, who refused to give his name, again plowed dirt with a refuge bulldozer Wednesday. He wouldn’t say why he was operating the machinery, but in several places, sagebrush and vegetation had been newly removed, leaving wide patches of bare mud within the complex.

The new road connects a bunkhouse with another road.