Blood-testing startup Theranos said it sent doctors and patients tens of thousands of corrected test results and voided data from its devices for 2014 and 2015, a devastating blow for the company that has come under scrutiny over the accuracy of its technology.

The Silicon Valley startup reported its testing-device problems to federal health regulators at the Centers for Medicare and Medicaid Services, the Wall Street Journal reported. A company spokeswoman confirmed the report.

Theranos is developing a technology that, the company has said, can run scores of diagnostic tests using only a few drops of blood. But the California-based startup has faced questions about whether its technology works, has endured multiple investigations, and its president has left the company.