Photo: The Canadian Press

SALEM, Ore. — The agency overseeing Oregon’s legal medical marijuana industry conceded in a report Thursday it has not provided effective oversight of growers and others in the industry, creating opportunities for weed to be diverted to the black market.

The blunt internal review echoes complaints from federal authorities that Oregon hasn’t adequately controlled its marijuana businesses and that overproduction of pot is feeding a black market in states that haven’t legalized it.

Oregon was one of the first states to legalize medical marijuana in 1998, and in 2014 voters approved allowing recreational use. The state’s struggle to transform a business that for decades had operated illegally in the shadows into a regulated industry sets an example for other states moving toward legalization.

Oregon Health Authority Director Patrick Allen ordered the internal review amid complaints from state and local law enforcement officials about lack of oversight of the pot industry. The health authority directs the state’s Medical Marijuana Program, while the Liquor Control Commission regulates recreational pot.

The review showed there were more than 20,000 grow sites, but only 58 inspections were carried out in 2017.

The Oregon Medical Marijuana Program has far too few inspectors, while the tracking of growers and the pot they produce has been inadequate and inaccurate, the report concluded.

“Potentially erroneous reporting coupled with low reporting compliance makes it difficult to accurately track how much product is in the medical system,” the report said. “This limits OMMP’s ability to successfully identify and address potential diversion.”

The report said the medical marijuana oversight agency lacks reliable, independent tools to validate grow site locations and relies on inconsistent county databases.

Law enforcement authorities say they often have trouble identifying which marijuana growers are legal. Seen from a helicopter just before harvest season, marijuana grows are like a green patchwork across one southwestern county, one drug enforcement officer recalled.