BRISTOL, Wis. — The drug bust shattered the early-morning stillness of this manicured subdivision in southeastern Wisconsin. The police pulled up outside a white-shuttered brick condo, jolting neighbors out of their beds with the thud of heavy banging on a door.
What they found inside was not crystal meth or cocaine or fentanyl but slim boxes of vaping cartridges labeled with flavors like strawberry and peaches and cream. An additional 98,000 cartridges lay empty. Fifty-seven Mason jars nearby contained a substance that resembled dark honey: THC-laced liquid used for vaping, a practice that is now at the heart of a major public health scare sweeping the country.
Vaping devices, which have soared in popularity as a way to consume nicotine and THC, the psychoactive ingredient in marijuana, have been linked in the last several months to nearly 400 illnesses and six deaths. State and federal health investigators have not yet determined a cause, but authorities are focusing on whether noxious chemicals have found their way into vaping supplies, perhaps from a flourishing nationwide black market of vaping products fueled by online sales and lax regulation.
The bust this month in Wisconsin, where THC is illegal, offers an intimate look at the shadowy operations serving large numbers of teenagers and adults around the country who are using black-market vaping products, sometimes unknowingly because it is difficult to tell them apart from legitimate ones.
“When we walked in there, we were like, ‘Oh boy,’” said Capt. Dan Baumann of the Waukesha Police Department. “This is what we were looking for, but we did not know it was this big.”
Key players in the operation, authorities said, were brothers barely into their 20s, Jacob and Tyler Huffhines, who lived in a small town nearby. Both are now in custody at the Kenosha County Jail. More arrests and charges in the case are likely to follow, according to the police.
Tyler, 20, is being held on charges of the manufacture, distribution or delivery of marijuana; Jacob, 23, is being held on charges of cocaine possession and of being a felon in possession of a firearm. Authorities said that Jacob was being investigated for his involvement in the drug operation.
Across the country, public health officials are awakening to a massive underground market for illicit vaping products, both for nicotine and for marijuana. The products are sold online and on the streets, in pop-up stores and individual transactions, sometimes arranged through social media.
“I’d meet people at Starbucks, a cross street, in front of an apartment, wherever they tell you,” said a 17-year-old who was one of the people hospitalized for the vaping-related lung illness in New York state. He asked that his name not be used to guard his reputation and privacy.
“It never comes up where they source it,” he said. “You don’t ask.”
Investigators have not determined whether there is a connection between the Wisconsin operation and any of the cases of severe lung diseases linked to vaping. But public health officials across the country, including Mitch Zeller, director of the Center for Tobacco Products for the Food and Drug Administration, say that street-made vaping products should be avoided by all consumers and pose the greatest health risk.
Vaping works by heating liquid and turning it into vapor to be inhaled. The original intent was to give smokers a way to satisfy their nicotine cravings without inhaling the carcinogens that come with burning tobacco.
But vaping devices and cartridges can be used to heat many substances, including cannabis-based oils, and some of the solvents used to dissolve them can present their own health problems.
On Wednesday the Trump administration said it planned to ban most flavored e-cigarettes and nicotine pods — including mint and menthol, in an effort to reduce the allure of vaping for teenagers. But the move may expand underground demand for flavored pods. And it does nothing to address the robust trade in illicit cannabis vaping products.
The Wisconsin operation is wholly characteristic of a “very advanced and mature illicit market for THC vape carts,” said David Downs, an expert in the marijuana trade and the California bureau chief for Leafly, a website that offers news, information and reviews of cannabis products. (‘Carts’ is the common shorthand for cartridges.)
“These types of operations are integral to the distribution of contaminated THC-based vape carts in the United States,” Mr. Downs said.
They are known as “pen factories,” playing a crucial middleman role: The operations buy empty vape cartridges and counterfeit packaging from Chinese factories, then fill them with THC liquid that they purchase from the United States market. Empty cartridges and packaging are also available on eBay, Alibaba and other e-commerce sites.
The filled cartridges are not by definition a health risk. However, Mr. Downs, along with executives from legal THC companies and health officials, say that the illicit operations are using a tactic common to other illegal drug operations: cutting their product with other substances, including some that can be dangerous.
The motive is profit; an operation makes more money by using less of the core ingredient, THC — which is expensive — and diluting it with oils that cost considerably less.
Public health authorities said some cutting agents might be the cause of the lung illnesses and had homed in on a particular one, vitamin E acetate, an oil that could cause breathing problems and lung inflammation if it does not heat up fully during the vaping aerosolization process.
Medium-grade THC can cost $4,000 a kilo and higher-grade THC costs double that, but additives may cost pennies on the dollar, said Chip Paul, a longtime vaping entrepreneur in Oklahoma who led the state’s drive to legalize medical marijuana there.
“That’s what they’re doing, they’re cutting this oil,” he said of illegal operations. “If I can cut it in half,” he described the thinking, “I can double my money.”
The black market products come packaged looking as the THC vaping products that are legal in some states do. Sometimes the packages are direct counterfeits of mass-market brands sold in places like California or Colorado, where THC is legal, and others just look the part.
“Someone would not recognize that this is not a legitimate product,” said Dr. Howard Zucker, commissioner of the New York State Department of Health, adding that this is a tremendous risk. “The counterfeit handbag you buy on the corner is not going to kill you but the counterfeit vaping device you buy has a chance to kill you,” he said.
In Wisconsin, the neatly packaged vaping devices had logos such as Dabwoods, Chronic Sour Patch and Dank King Louie. The police say the Huffhines operation produced close to 3,000 cartridges a day. Cartridges sell for around $35 to $40.
A lawyer for Tyler Huffhines declined to comment.
Wisconsin police say they were stunned by the scope and ambition of the Huffhines operation, and only beginning to understand how far it might have reached.
It was a teenager in nearby Waukesha whose actions eventually led the police to the operation in Bristol, a town just miles from the Illinois border.
That teenager’s parents discovered that he was vaping and brought him to the police station in Waukesha. He then told the police where he got his vaping supplies; the authorities traced the sellers step by step, and several degrees of separation later, they were led to the Huffhines brothers.
The condo in Bristol, rented under a false name, was believed to be their base of operations. But on an afternoon this past week, it appeared deserted, with the blinds inside closed tightly and a dent on the front door.
Until recently, the condo hummed with quiet activity that attracted only glancing notice from neighbors. The operation employed at least 10 people, the police said, who were paid $20 an hour to use syringes to fill cartridges with oil. The Huffhineses kept meticulous records, using timecards to note when employees worked. The cartridges were sold in packs of 100, through channels that authorities, who also seized 18 pounds of marijuana and three money-counting machines, said they did not yet fully understand.
It might have been the perfect place for a drug operation, said one neighbor, who described the subdivision as a mix of busy professionals and families who do not socialize much.
Another neighbor said she had thought that the Huffhines brothers had begun renting the place a few months ago, describing a steady stream of young men in and out of the condo, usually neatly dressed, and driving expensive cars.
“I can’t give my name,” she said, lowering her voice. “These are drug lords.”
Inside the Huffhines’ home in the nearby Paddock Lake community, a five-minute drive from the condo, investigators last week found $59,000 in cash, eight guns, 10 grams of marijuana, as well as scales and other drug-related paraphernalia.
At Westosha Central High School, which the Huffhines brothers had attended, they were seen as ambitious and privileged, living with their mother, a real estate agent, and grandfather in a quiet neighborhood overlooking a lake.
Students leaving school Thursday afternoon described a system of easy access to vaping devices that contain nicotine or THC, despite strict penalties from administrators if they are caught.
Students frequently vape in the bathrooms, they said, and obtaining vaping devices is as simple as asking someone for a contact.
News about deaths and injuries from vaping has been spreading throughout school, a 16-year-old said.
“People are scared of getting caught,” he added. “Now they’re scared of getting sick, too.”