US health officials have ordered a startup headed by the ex-wife of a Google co-founder to halt a service of DNA testing to determine health risks.

The Food and Drug Administration said in a warning letter made public Monday to the company, 23andMe, that its "saliva collection kit and personal genome service" needs to get regulatory approval.

The company was co-founded by Anne Wojcicki, who recently split with Sergey Brin, one of the co-founders of Google. The Internet giant had been an investor in the firm.

The company provides a saliva analysis kit aimed at helping customers determine their genetic risks for diseases such as diabetes, coronary heart disease, and breast cancer.

The FDA letter said that most of the uses for the kit make it a "medical device" which requires regulatory approval.

The letter said some uses of the kit "are particularly concerning," because of "potential health consequences" of false positive or false negative results for some conditions such as genetic predisposition for breast cancer.

"For instance, if the (genetic) risk assessment for breast or ovarian cancer reports a false positive, it could lead a patient to undergo prophylactic surgery, chemoprevention, intensive screening, or other morbidity-inducing actions, while a false negative could result in a failure to recognize an actual risk that may exist," the letter said.

The letter noted that "even after these many interactions with 23andMe, we still do not have any assurance that the firm has analytically or clinically validated the (kit) for its intended uses."

As a result, "23andMe must immediately discontinue marketing the (kit) until such time as it receives FDA marketing authorization for the device."

The company describes itself as "the leading personal genetics company dedicated to helping individuals understand their own genetic information through DNA analysis technologies and web-based interactive tools."

It has received financial backing from Google Ventures, Johnson & Johnson Development Corporation, The Roche Venture Fund and others.

Kendra Cassillo, a spokeswoman for 23andMe, said the company had received the warning letter.

"We recognize that we have not met the FDA's expectations regarding timeline and communication regarding our submission," she said in an email.

"Our relationship with the FDA is extremely important to us and we are committed to fully engaging with them to address their concerns."

There was no immediate comment from Google.