Trump administration scientists told senators Tuesday a replacement for a malfunctioning COVID-19 test will be available by the end of this week, with new supplies for every state public health lab and commercial lab kits that could administer up to one million tests.

But some lawmakers at a Senate Committee on Health, Education, Labor, and Pensions hearing — such as ranking member Patty Murray, D-Wash. — were skeptical.

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“Frankly, I’m hearing from professionals that’s unrealistic,” said Murray, who represents Washington state, the site of a coronavirus cluster at a facility that treats the elderly. Nine Washington residents have died, according to the Washington State Department of Health.

The flawed diagnostic test developed by the Centers for Disease Control and Prevention delayed the ability of health professionals to accurately detect and contain the virus for nearly the entire month of February.

That hurt the ability of health professionals and patients to contain exposure to a potential pandemic.

“We developed the test very quickly and then detected some problems when the quality control steps were measured,” testified CDC Principal Deputy Director Anne Schuchat.

Asked if the U.S. will be able to expand testing enough to curb the evolving disease, Schuchat did not give a firm answer.

“I am optimistic but I want to remain humble, because we see in emerging infectious diseases . . . surprises,” Schuchat said.

CDC is working on remanufacturing the test kit, according to Department of Health and Human Services testimony. The hearing comes one day after the CDC abruptly canceled a national press call and deleted data about the number of people tested from its website.

The scramble to develop a test came after China posted genome sequences in early January of the novel coronavirus that causes COVID-19. Within a week, the CDC developed a test to diagnose the novel coronavirus in respiratory samples. On Feb. 3, it asked the FDA to work with private companies to manufacture and ship the CDC-developed test kit under authority granted in emergencies.

On Feb. 5, the kits began shipping. It took until Feb. 27, after media outlets reported concerns from professionals at state and local health labs who were unable to get conclusive results, that the CDC began shipping new test kits.

Schuchat emphasized that although each state should get new tests, public health labs only perform a small number of overall tests.

Clinical labs have tested over a million specimens for flu this year, while public health labs have tested just 62,000 specimens, she said.

“Public health labs are a tiny piece of the testing world,” said Schuchat.

At the same hearing, Food and Drug Administration Commissioner Stephen Hahn said that commercial labs could be equipped by the end of the week with 2,500 kits, which could administer up to one million tests. Each patient takes multiple tests to confirm the diagnosis.

When pressed by senators such as Murray, Hahn declined to say how many people he expected to be tested this week.

The FDA is working with the company Integrated DNA Technologies, Inc., on the test kits, according to an FDA spokesperson.

The U.S. remains months away from developing a test with more immediate results at the point they come into a doctor’s office with symptoms like fever and a cough, according to Robert P. Kadlec, the HHS assistant secretary for preparedness and response.

Those symptoms are commonly experienced by people with the flu as well as COVID-19, and the only surefire way to distinguish between the two is through a diagnostic test, Anthony S. Fauci, head of the National Institute of Allergy and Infectious Diseases, told the panel.

The CDC has faced criticism in recent days for the manufacturing issues in its COVID-19 tests. Schuchat responded to the criticisms in part by emphasizing that while CDC supplies test kits to public labs, it’s up to the Biomedical Advanced Research and Development Authority, another part of HHS, and the FDA to scale up testing to the majority of the country’s labs.

Compared to influenza, the personnel and resources the CDC devotes to coronaviruses are “relatively small,” Schuchat said, and the CDC will not be able to sustain its COVID-19 response without an appropriation of new funding from Congress.

Schuchat and Fauci joined Vice President Mike Pence, who is leading the outbreak response, in closed-door luncheon meetings with senators Tuesday afternoon.