The controversial blood-testing startup ran into trouble late in 2015 after The Wall Street Journal launched a series of pieces that questioned the company's finger-prick blood testing technology.
Now, The Journal reports that the Centers for Medicare and Medicaid Services (one of the federal bodies that regulates laboratory blood tests) found problems with Theranos' laboratory in Newark, California, which could put the company's relationship with the Medicare program in jeopardy.
Citing people familiar with the matter, The Journal reports that the problems observed by CMS health inspectors were more serious than the agency's inspection in 2013. It's unclear what the exact problems were.
The results from the inspection are expected to be released to the public soon, The Journal said.
A Theranos representative told the Journal that company has yet to see the CMS report cited by the newspaper.
Business Insider has reached out to Theranos for comment.