The U.S. Food and Drug Administration has warned 23andMe Inc, a company backed by Google Inc, to halt sales of its genetic testing services because they have not received regulatory clearance.

23andMe, which was founded in 2006 by Anne Wojcicki with the backing of Google, sells DNA testing services that the company says detect a range of genetic mutations and provide information about a person's health risks. Wojcicki recently separated from her husband, Sergey Brin, a co-founder of Google.

In a warning letter dated November 22 and released on Monday, the FDA said it considers the company's product a medical device that therefore requires regulatory clearance, "as FDA has explained to you on numerous occasions."

The privately held company, which is based in Mountain View, California, did not immediately respond to a request for comment left before business hours.

The FDA said some of the intended uses of the company's Saliva Collection Kit and Personal Genome Service (PGS) are particularly concerning, including risk assessments for certain cancers.

The agency said that if the company's risk assessment for breast or ovarian cancer reports a false positive, it could lead a patient to undergo preventative surgery, intensive screening or other potentially risky procedures. A false negative, on the other hand, could result in a failure to recognize actual risk.

The FDA said in its letter that the company submitted applications in July and September of 2012 for several of these indications for use.

"However," the FDA said, "to date your company has failed to address the issues described during previous interactions with the Agency" or provided additional information requested. As a result, the FDA said the applications "are considered withdrawn."

The agency said it had been "diligently working" to help the company comply with the law, and has spent significant time evaluating the intended uses of the product. It said it also provided detailed feedback to the company regarding the types of data it needed to submit. The agency said its interactions with the company included more than 14 face-to-face and teleconference meetings, hundreds of email exchanges, and dozens of written communications.

"However, even after these many interactions with 23andMe, we still do not have any assurance that the firm has analytically or clinically validated the PGS for its intended uses," the FDA said.

The company's name refers to the 23 pairs of chromosomes that make up each individual's genome.