U.S. health officials now advise those who use Zantac to treat heartburn to consider other medicinal alternatives.

On Wednesday, The US Food and Drug Administration said it is recalling Zantac due to possible contamination by a human carcinogen, which is a substance that may cause cancer.

Nationwide, retailers were asked to pull all prescription and over-the-counter ranitidine drugs, known by the brand name Zantac, from the market immediately.

FDA is requesting immediate removal of all Rx and over-the-counter ranitidine (Zantac) from the U.S. market. https://t.co/gta7J4XGrM pic.twitter.com/LG9CBQ0BVT

— U.S. FDA (@US_FDA) April 1, 2020

The FDA noted that an investigation into the product that began in 2019 has finally revealed that levels of a contaminant in the heartburn medications increase over time and when stored at higher-than-normal temperatures, pose a risk to public health.

The carcinogen that was found in some of the drugs is called N-nitrosodimethylamine or NDMA.

"We didn't observe unacceptable levels of NDMA in many of the samples that we tested," Dr. Janet Woodcock, director of the FDA's Center for Drug Evaluation and Research, said in Wednesday's announcement.

"However, since we don't know how or for how long the product might have been stored, we decided that it should not be available to consumers and patients unless its quality can be assured," Woodcock said in part. "The FDA will continue our efforts to ensure impurities in other drugs do not exceed acceptable limits so that patients can continue taking medicines without concern."

According to the FDA's announcement, letters are now being sent to all manufacturers of ranitidine requesting that they withdraw products from the market, and consumers are advised to stop taking any ranitidine tablets or liquid medications they currently have. The FDA said to dispose of them properly and not buy more.

Due to the coronavirus pandemic, the FDA said don't return your medicines to a "drug take-back location," but rather follow disposal instructions in the medication guide or insert -- or follow the FDA's recommended safe disposal steps on its website.