Regulators are examining a possible link between homeopathic teething products and hundreds of instances of fever, vomiting, and other side effects in children and babies who have taken them over the past six years—and at least 10 deaths, Bloomberg reports.

Food and Drug Administration officials have been looking into the potential health risks of homeopathic teething tablets and gels. On September 30, the agency recommended that consumers stop using a number of such products distributed by chains like CVS cvs and Hyland’s while noting that a direct cause-and-effect has yet to be definitively established.

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“Teething can be managed without prescription or over-the-counter remedies,” said Dr. Janet Woodcock, director of the FDA’s Center for Drug Evaluation and Research, in a statement. “We recommend parents and caregivers not give homeopathic teething tablets and gels to children and seek advice from their health care professional for safe alternatives.”

Homeopathy is a controversial form of alternative medicine predicated on the theory that highly diluted doses of natural substances that might cause symptoms of a disease can be used to treat those same conditions. It has no basis in conventional medical science and some countries have considered blacklisting the practice.

The FDA must still do more research into the potentially problematic teething products before coming to a clear-cut answer, it told Bloomberg. “It is important to note that while adverse event reports give us some information about a product and serious injuries or deaths related to use of a particular product, they often indicate situations that require additional analysis and do not constitute conclusive evidence of a problem with the product,” the agency said.

Still, CVS decided to voluntarily remove its homeopathic teething products from shelves following the FDA’s September warning. Hyland’s has also decided to discontinue distribution of such medicines, but stressed in a statement Tuesday that the company is “confident that any available Hyland’s teething products, including those you already have, are safe for use.”