The US Centers for Disease Control and Prevention has not yet returned to shipping coronavirus test kits to state labs after some tests were initially found to be faulty, Dr. Nancy Messonnier, director of CDC’s National Center for Immunization and Respiratory Diseases, said Friday during a call with reporters.

The CDC wants to make sure that “every T is crossed before we put these kits back out, so we’re taking a little extra time here,” Messonnier said. She declined to give a specific timeline.

Why this matters: Earlier this week, the agency said some state labs had been unable to validate the test. The CDC is now remanufacturing a reagent used in the test that was yielding “indeterminate answers,” Messonnier said.

"What we’re doing at CDC is reformulating those reagents,” she said, "and we are moving quickly to get those back out to our labs” with state and local partners.

Before it began shipping these kits, the CDC was the only lab in the United States that could test for the virus. Experts say the new test kits open the door to confirming cases earlier, thus being able to take swift action to contain any further spread in the United States.

The CDC had previously announced plans to ship roughly 200 test kits to domestic labs and another 200 to international labs. Each test kit can perform 700 to 800 patient samples.