In only two years, a small, colorful vaping device called Elf Bar has become the most popular disposable e-cigarette in the world, generating billions in sales and quickly emerging as the overwhelming favorite of underage U.S. teens who vape.

Last week, U.S. authorities publicly announced the first seizure of some of the company’s products, part of an operation confiscating 1.4 million illegal, flavored e-cigarettes from China. Officials pegged the value of the items at $18 million, including brands other than Elf Bar.

But the makers of Elf Bar and other Chinese e-cigarettes have imported products worth hundreds of millions of dollars while repeatedly dodging customs and avoiding taxes and import fees, according to public records and court documents reviewed by The Associated Press.

Records show the makers of disposable vapes routinely mislabel their shipments as “battery chargers,” “flashlights” and other items, hampering efforts to block products that are driving teen vaping.