Brendan McDermid | Reuters

The sleek Juul electronic cigarettes have become a phenomenon at U.S. high schools, vexing educators and drawing regulatory scrutiny over their sweet flavors and high nicotine content. Now, a new wave of lower-priced Juul knock-offs is showing up at convenience stores, vape shops and online - despite a U.S. Food and Drug Administration rule banning the sale of new e-cigarette products after August 2016 without regulatory approval. Start-ups and major tobacco firms have launched more than a dozen new high-nicotine devices with Juul-like designs since the FDA imposed the deadline, according to a Reuters review of the companies' online advertisements, social media posts and public statements. The FDA earlier this month threatened to ban Juul and four other leading vaping products unless their makers take steps to prevent use by minors. But the warning came after companies introduced a slew of new Juul copycats following the August 2016 deadline with no regulatory consequences.

In a statement to Reuters, the agency said it was investigating whether certain brands are being improperly sold without FDA approval and that it "plans to take additional action on this front very soon." The agency said it would focus on products with high-nicotine concentrations and flavors appearing to target young people, and take "swift action wherever appropriate." The FDA set the August 2016 deadline to rein in the fast-growing industry but allowed sales of Juul and other older devices to continue without regulatory approval until 2022. The companies that started marketing new devices after the deadline include startup firms such as Kandypens, Myle Vapor and VGOD, as well as large multinational tobacco companies including British American Tobacco Plc and Imperial Brands Plc. Kandypens touted its new Rubi vaping device last October - more than 14 months after the August 2016 cutoff - with an Instagram post saying it had been "working hard over here for the last 12 months" on the product. Vaping distributor VGOD posted on its website in May that it was "an honor to finally introduce the STIG," referencing its Stig Pods, a disposable three-pack of high-nicotine devices. British American Tobacco chief executive Nicandro Durante said on a July 2018 earnings call that the company would be launching its higher-nicotine Vuse Alto product in the United States the following month. Imperial Brands announced its myblu brand of e-cigarettes in a February 2018 press release. Kandypens, Myle and VGOD did not respond to requests for comment. Spokespeople for Imperial Brands and British American Tobacco said their products were compliant and on the market before August 2016. Imperial Brands said it had purchased an existing e-cigarette brand and renamed it. British American Tobacco did not respond to questions about its marketing or sales. A spokeswoman for Juul Labs, Victoria Davis, said the company is cooperating with regulators and working to prevent underage use of a product designed to help adult smokers quit tobacco cigarettes. "No minor or non-nicotine user should ever try Juul," Davis said. 'Frozen mystery pop' E-cigarettes vaporize a liquid that contains nicotine, the addictive stimulant that gives smokers a rush. The Juul design mimics a flash drive - with plug-in cartridges of concentrated nicotine juice. It is far more compact than earlier vaping devices and produces less vapor, making it easy to use without being detected - an attribute some health advocates say attracts teenagers. Juul's imitators are also small and compatible with higher-nicotine blends, though some can also be filled with lower-strength juice. The Chinese company Suorin introduced several such devices to the United States over the past year. Many high-schoolers and college students said they have switched to these products because buying widely available nicotine liquids is less expensive than Juul pods. In a statement, Suorin said it didn't have "clear guidance" from the FDA on regulations governing its newer products but hopes to better understand how to fully comply. The company said its products are only intended for adult smokers. One Juul pod has the nicotine content of about 20 cigarettes – the number in a traditional pack – according to Juul's marketing. A pod can be consumed in a day by a heavy user, according to interviews with Juul customers. Many of the newest blends from Juul and its imitators - called "nicotine salts" in the industry - contain a compound called benzoic acid, which lowers the pH level of the liquid. That reduction allows users to take in more nicotine without a bitter taste, according to the U.S. Centers for Disease Control and Prevention (CDC). In addition to the devices, dozens of high-nicotine e-liquids have arrived on the market with names such as "frozen mystery pop," "rainbow drops" and "Tokyo chocolate banana," which critics say are designed to attract young customers. Vaping proponents argue the Juul and similar new products give cigarette smokers looking to quit a much better option than lower-nicotine e-cigarettes. "It gives the same exact sensation as a cigarette, except you don't wake up coughing at 2 a.m.," said Charles Trejo, a manager at V for Vape, a Los Angeles retailer. Public health researchers say high-nicotine vaping devices like the Juul have proven adept at drawing in new customers, including teenagers, who never used tobacco. "What they're doing is creating addicts in large numbers," said Dr. Robert Jackler, a professor who heads a group studying the impact of tobacco advertising at Stanford University. High-nicotine vaping devices amount to a "weaponization" of the drug, he said, citing research showing young people are particularly susceptible to nicotine addiction, which could lead them to other addictions including cigarettes.