Federal regulators say that kombucha—a recently popularized, rather expensive fermented tea—contains more alcohol than some of its producers claim, and have issued formal letters out of concern for the proper enforcement of warning labels, minimum age requirements and special taxes. The Alcohol and Tobacco Tax and Trade Bureau says that in some brands of kombucha, it has found alcohol levels above .5 percent, which is the U.S. dividing line between alcoholic and nonalcoholic drinks.

Kombucha producers don’t agree, to say the least. “Nobody’s saying, ‘Let me get a six-pack of kombucha and get wasted tonight,’” the president of Kombucha Brewers International tells The Wall Street Journal.

This isn’t the first time concerns have been raised surrounding the alcoholic content of the bottled probiotic beverage: In 2010, Whole Foods briefly removed kombucha from its stores in response to concerns about alcohol levels. These days, Whole Foods stocks brands like GT’s Kombucha again—but not before the company re-formulated to offer both alcoholic and non-alcoholic variants of its signature tea.

In California, two consumer complaints seeking class action status were filed last month, each alleging that Millennium Products Inc., the producer of the popular GT’s, Kombucha, has been engaging in deceptive alcohol-content labeling. One lawsuit claims the bubbly drink has alcohol levels of up to 3.8 percent, compared with about 5 percent you can expect in most beers. Kombucha producers have fired back, saying that these reported levels are the result of unsophisticated testing that can’t properly distinguish between the acid in kombucha and actual alcohol.

H/T The Wall Street Journal