The FBI raided microbiome testing startup uBiome's San Francisco offices on Friday.

The Wall Street Journal, which first reported on the raid, reports that the FBI is investigating uBiome's billing practices.

CNBC reports that uBiome routinely charged patients twice for tests.

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The FBI on Friday raided the San Francisco offices of uBiome, a startup that sells tests that sequence the microbiome, or the assortment of bacteria and other microbes that live in our bodies.

The Wall Street Journal, which first reported on the raid, reported that the FBI is investigating uBiome's billing practices.

UBiome sent Business Insider this statement: "We are cooperating fully with federal authorities on this matter. We look forward to continuing to serve the needs of healthcare providers and patients."

The FBI confirmed that its agents were "conducting court-authorized law enforcement activity" at the address of uBiome's headquarters, but declined to provide further information.

UBiome sells doctor-ordered tests including SmartJane, its test that looks at the vaginal microbiome to test for sexually transmitted diseases as well as chronic vaginal infections, and SmartGut, which looks at the gut microbiome to test for gut conditions and metabolic disorders. Both can be covered by health insurance. uBiome also sells a direct-to-consumer test that doesn't require a prescription called the "Explorer" test.

Read more: I tried a test that let me peek inside my microbiome, the 'forgotten organ' that scientists say is the future of medicine — and what I learned shocked me

CNBC reports that uBiome routinely charged patients' plans twice for tests. CNBC also reported that health insurer Anthem had flagged the company for its over-billing practices. Anthem did not immediately return a request for comment.

Scientists have been working on ways to use the microbiome to unlock new treatments for difficult diseases. It's led to new companies — both on the medical side and in agriculture— that are taking a range of approaches to looking at the microbiome. It's often seen as the "forgotten organ."