When the FDA issued a bulletin alerting everyone to the presence of a possible cancer-causing impurity in the popular heartburn drug marketed as Zantac, the administration stopped short of telling people to stop taking the popular drugs. Now, in the wake of that news, shipments of a generic version of the drug are being halted.

In its release, the FDA noted that samples of the drug known as ranitidine, also sold under the brand name Zantac, tested positive for a potentially cancer-causing agent called N-nitrosodimethylamine, or NDMA. Levels of the carcinogen weren’t alarmingly high, but its presence alone was enough to warrant a public alert.

Pharmaceutical company Novartis decided that the FDA’s findings were enough to put the brakes on its distribution of the generic version of the drug, noting that it would stop its shipments while it waits for “further clarification” and conducts its own internal investigation.

NDMA is a probable human carcinogen, meaning that it’s likely that it has the potential to cause cancer in humans. It’s a byproduct of industrial processes, and is unfortunately common in many processed foods. It’s thought to be dangerous in high amounts, and the levels detected by the FDA in ranitidine are comparable to levels you might find in food.

It’s important to note that there is no official recall or ban on the sale of Zantac or the generic forms of the drug, and you’ll still find it lining the shelves of your local drug store. That being said, a similar situation recently occurred with blood pressure and heart medication, with cancer-causing impurities found in popular drugs that ultimately warranted recalls, and it’s not a stretch to think that the same thing might eventually happen with ranitidine.