YANJI, China — After the North Korean coal mine where she worked stopped paying salaries, Park Kyung Ok tried her hand at business.

Buttons and zippers, candy and dried squid, fabric, plastic tarpaulins, men's suits and cigarettes.

"I sold just about everything," said Park, 44.

But it wasn't until she started hawking methamphetamine in 2007, she said, that she was able to earn a living.

Methamphetamine, known as orum, or "ice," is a rare commodity manufactured and sold in North Korea, where most factories sit idle, the equipment rusted or looted. The North Korean government once produced the drug, and others that are illicit in the West. Resourceful entrepreneurs have since set up their own small facilities, and evidence suggests that they are distributing the drug beyond the nation's borders.

Last month, five alleged drug smugglers — Chinese, British and Thai men among them — appeared in federal court in New York, extradited from Thailand in a plot to smuggle 220 pounds of crystal meth to the United States. They said that their product originated in North Korea.

A Harvard University researcher, Sheena Chestnut Greitens, has tracked 16 drug busts from 2008 to the present in China involving crystal meth from North Korea in quantities of up to 22 pounds.

"Meth is a product you can make in bathtubs or trailers," Greitens said. "You have a wide range of people involved in production and trafficking."

Park, a bantam-size woman who tittered nervously when recounting her own audacity, said she got into the meth business fresh from a divorce, while struggling to support her children and a disabled sister in Hoeryong, a hardscrabble mining town of 130,000 on the Chinese border.

Park used to travel to another North Korean city, Chongjin, to buy meth that she would carry back hidden in a candy box. She would sell it behind the counter at a bicycle parts store at the public market. Hidden among the spare parts were metal plates, burners and other drug paraphernalia.

She usually paid the equivalent of $15 for a gram of high quality product, which she would then cut with cheaper meth and divide into 12 smaller portions to resell for a few dollars' profit.

"It was just enough money that I could buy rice to eat and coal for heating," said Park, who was interviewed recently in China and, like most North Korean defectors, used an assumed name.

North Koreans say there is little stigma attached to meth use. Some take it to treat colds or boost their energy; students take it to work late. The drug also helps curb appetites in a country where food is scarce. It is offered up as casually as a cup of tea, North Koreans say.

"If you go to somebody's house it is a polite way to greet somebody by offering them a sniff," said Lee Saera, 43, of Hoeryong, also interviewed in China. "It is like drinking coffee when you're sleepy, but ice is so much better."

Despite its draconian legal system, North Korea has long been easygoing about narcotics use. With analgesics scarce, opium paste is commonly sold for pain relief. Marijuana (called "mouth tobacco") is legal and frequently grown at home to be mixed in with rolling tobacco.

Methamphetamine is a synthetic drug that was first developed in Japan in the late 19th century, made from chemicals such as ephedrine and distributed as a stimulant.

Through the 1990s, the North Korean government ran the production of opium, meth and other drugs for Office 39, a unit raising hard currency for late leader Kim Jong Il, according to narcotics investigators. But the North Korean government has largely gone out of the drug business, according to the U.S. State Department's 2013 International Narcotics Control Strategy Report.

When the North Korean government controlled the business, the drugs were strictly for export. Privatization made the drugs more widely available within North Korea. North Koreans say meth first appeared on the streets around 2005 and that it came from Hamhung, the onetime center of the nation's pharmaceutical and chemical industry, and thus a city filled with unemployed scientists and technicians. The industry then spread to Chongjin and the capital, Pyongyang.

"North Korean people learn fast to reuse their skills," said Kim Yong Chol, 58, a truck driver who fled North Korea in August.

Meth was ideal for budding North Korean entrepreneurs because it could be cooked in small "kitchen laboratories," with chemical precursors readily available across the border in China, which has laxer control than many other countries.