The contamination made the tests uninterpretable, and—because testing is crucial for containment efforts—it lost the country invaluable time to get ahead of the advancing pandemic.

The CDC had been vague about what went wrong with the tests, initially only saying that "a problem in the manufacturing of one of the reagents" had led to the failure. Subsequent reporting suggested that the problem was with a negative control—that is, a part of the test meant to be free of any trace of the coronavirus as a critical reference for confirming that the test was working properly overall.

Now, according to investigation results reported by The New York Times, federal officials confirm that sloppy laboratory practices at two of three CDC labs involved in the tests' creation led to contamination of the tests and their uninterpretable results.

Shortly after the problems became apparent in early February, the Food and Drug Administration sent Timothy Stenzel, chief of in vitro diagnostics and radiological health, to the CDC to investigate what was going wrong. According to the Times, he found a lack of coordination and inexperience in commercial manufacturing.