Some of the coronavirus testing kits distributed to state labs around the US do not work properly, according to the Centers for Disease Control and Prevention.

Some of the kits, which also were sent to at least 30 countries, produced “inconclusive” results because of flawed components — and the CDC said it planned to send replacements to make them work.

Since late January, the agency has rushed to distribute the kits to allow states to conduct their own, faster testing rather than ship all samples to its headquarters in Atlanta.

Speeding up the tests — which can be delayed by days if sent to Atlanta — is important given the CDC’s expectation that the virus will likely start spreading within US communities at some point.

It was not immediately clear how many kits were flawed.

Of six state health departments that responded to requests for comment by Reuters, half of them — including California and Georgia — said they were waiting for replacement components.

The states discovered the flaw during their quality-control verification process.

“When some states were doing this, we received feedback that they weren’t — that it wasn’t working as expected, specifically some public health labs at states were getting inconclusive results and what that means is that test results were not coming back as false positive or false negatives, but they were being read as inconclusive,” the CDC’s Nancy Messonnier told reporters Wednesday, according to CNN.

“We have multiple levels of quality control to detect issues just like this one,” Messonnier said. “We’re looking into all of these issues to understand what went wrong, and to prevent these same things from happening in the future.”

Other states, including Illinois, said the kits had produced accurate results and they were now conducting their own testing.

The problem is likely reagents, or enzymes, which are needed to carry out the tests, Messonnier said.

“Things may not always go as smoothly as we may like,” she said, adding that the CDC had not yet been invited to send experts to China as part of a World Health Organization team to investigate the outbreak, which has killed more than 1,300 people and infected well over 50,000.

Messonnier warned that at some point, the US was likely to see “community spread.”

“[We] can and should be prepared for this new virus to take a foothold in the US,” where there have been 14 confirmed cases so far, she told reporters.