Kombucha comes in many flavors, but its base is always the same, made by leaving a fungus of yeast and bacteria to ferment for several weeks in sugary tea. The resulting brew has some alcohol and tastes tart, vinegary and is slightly effervescent. It then often is made palatable by adding juice.
In order to maintain its probiotic benefits, kombucha is left unpasteurized, or raw, although some companies recently have started selling pasteurized varieties.
The problem with raw kombucha is that it may continue to ferment unless it is refrigerated. The U.S. Treasury, which oversees alcohol and tobacco taxation, recently warned consumers that kombucha bottles have been found that "significantly exceed" the allowed 0.5 percent.
Beverages with more than trace amounts of alcohol must carry warning labels, but their manufacturers also are subject to alcohol taxes.
The Treasury said it has sent samples from around the country to laboratories and is still awaiting results to determine the extent of the problem.
Art Resnick, a spokesman at the Alcohol and Tobacco Tax and Trade Bureau, told ABC News.com it's very rare that a drink comes under this kind of government scrutiny.
It's unclear how the recent wave of publicity will affect kombucha sales. Since the recalls, kombucha aficionados have banded together, exchanging home-brew recipes on chat boards and a kombucha Facebook page.
"The publicity hasn't hurt our relationship with consumers," said Kombucha pioneer Dave. "If anything, it has increased awareness of kombucha."