(CNN) Dr. Deborah Birx said that the White House coronavirus task force is missing 50% of the data for coronavirus tests that have been conducted.
Birx, one of the top officials on the White House's coronavirus task force, said Thursday that part of the $2 trillion economic stimulus measure that was signed into law by President Donald Trump requires that all tests conducted get reported to the Centers for Disease Control and Prevention. But Birx says she has not received that data yet.
"Well, I'm telling you, I'm still missing 50% of the data from reporting," she said. "I have 660 (thousand) tests reported in. We've done 1.3 million. ... So, we do need to see -- the bill said you need to report. We are still not receiving 100% of the tests."
When pressed about the possibility that 1 in 3 tests had produced false negatives, Birx said, "I haven't seen that kind of anomaly."
Birx added that "the number of positive tests is tracking very closely with a number of cases diagnosed."
The absent data underscores how issues surrounding testing -- including overall volume, public accessibility and timely processing -- have remained a steady component of the federal government's coronavirus response.
CNN reported Wednesday that New Jersey-based Quest Diagnostics, one of the nation's largest commercial labs, has faced a steep backlog of tests in the last two weeks, with about 160,000 coronavirus test orders -- about half the company's total -- waiting to be processed on March 25, and delayed results in some cases up to 10 days.
And despite the White House's announcement in mid-March that the federal government would partner with private companies to set up drive-thru coronavirus testing sites, the Department of Health and Human Services confirmed to CNN on Tuesday that among major retailers Target, Walgreens, Walmart and CVS, there are only five locations that are currently offering drive-thru testing -- none of which are open to the general public.
Governors in both red and blue states have also pushed back on the federal government's often-rosy assessment of the state of national testing efforts.
The New York Times reported Monday that Trump said on a call with governors, "I haven't heard about testing in weeks," and "I haven't heard about testing being a problem" in response to a comment by Montana Gov. Steve Bullock, a Democrat, who said states lack adequate tests.
"Yeah, that's just not true," Maryland Republican Gov. Larry Hogan told NPR on Tuesday when asked about Trump's assertion.
"I mean, I know they have taken some steps to create new tests but they are not actually produced and distributed out to the states," Hogan added. "So it is an aspirational thing and they've got some new things in the works, but they are not actually out on the streets and no states have enough testing."
Rhode Island Democratic Gov. Gina Raimondo told CNN on Monday regarding the President's comments that governors are "all continuing to struggle with testing, testing supplies and also procuring (personal protective equipment), and that's a pretty regular refrain that all of the governors have when we talk to each other and when we talk to the President."
Birx's announcement came after Trump told reporters earlier on Thursday that he had tested negative for coronavirus for the second time after taking a new test that provides results in 15 minutes. Trump said he had taken the test "really out of curiosity to see how quickly it worked, how fast it worked."
"I just took it this morning. And I took it, it took me literally a minute to take it and it took me -- I guess it was 14 or 15 minutes" for results, Trump said. "I went to work, I didn't wait for it, but it said it took 14 minutes or something with a conclusion and it said the President tested negative for Covid-19."
This story has been updated with background and more details.