WASHINGTON – The test kits for detecting the nation's earliest cases of the novel coronavirus failed because of "likely" contamination at the Centers for Disease Control and Prevention, whose scientists did not thoroughly check the kits despite "anomalies" during manufacturing, according to a new federal review.

The review, conducted by two Department of Health and Human Services lawyers, also said there was "time pressure" at the CDC to launch testing, and "lab practices that may have been insufficient to prevent the risk of contamination." The lawyers, from the department's general counsel's office, were not named.

Neither the review nor an accompanying statement from President Donald Trump's chief spokesman at HHS assigned blame to any CDC scientist or official by name.

The review is the first confirmation by the Trump administration that the original test kits were likely contaminated, and that the problem appeared to have occurred in late January within the CDC's headquarters in Atlanta. In general, HHS has defended the administration's efforts to counter the pandemic.

The three-page review also acknowledged that, after weeks of delay, the likely contamination ultimately prompted the CDC to jettison a problematic component of the test kit. The component was intended to detect coronavirus strains other than the one that causes COVID-19, the disease that has killed more than 117,000 Americans.

The Washington Post reported on April 18 that the test kits had generated false-positive results — caused by the CDC's contamination — at 24 of the first 26 public health labs that tried them out before analyzing samples from actual patients. The Post also reported that an examination by the Food and Drug Administration had concluded that the tests failed because of substandard manufacturing practices and that the CDC violated its own laboratory protocol in making the kits.

The false positives arose during testing of "negative control" samples that contained highly purified water and no genetic material. That aspect of testing was essential to confirm that results would be reliable and not skewed by contamination.

A spokesman for the CDC did not immediately respond to a request for comment on the HHS review. The review was first reported Friday by Sinclair Broadcast Group.

The CDC's failure with the test added many weeks of delays to the rollout of widespread testing and hampered efforts by state and local public health labs to minimize harm before the coronavirus became widely established in the United States.

The review was based on the HHS lawyers' interviews "with nine CDC employees and contractors who were involved in the production of the test kits." The lawyers also spoke with Timothy Stenzel, a top FDA official regulating diagnostic devices used for medical treatment, and "one other FDA scientist in a consulting capacity," according to the review.

The review identified several CDC labs involved with making the test kits. It said it was "possible" that contamination occurred during production of materials for the kits performed by the Biotechnology Core Facility Branch, known as the core lab.

But the review noted that the core lab "took extreme precautionary measures … to minimize any risk of contamination." The contamination "most likely" occurred in CDC's Respiratory Virus Diagnostic Lab, during its processing and testing of the materials produced by the core lab, the review said.

"It was at this stage of the manufacture, when the bulk reagent materials for the test kits were processed and tested at [the respiratory virus lab], that they were most likely exposed to positive control material," the review said.

According to the review, the respiratory lab "had already made multiple uses of positive control material at the time bulk test kit reagents were being handled, increasing the opportunities for contamination."

The review also said that "a number of CDC interviewees and Dr. Stenzel of FDA described lab practices that may have been insufficient to prevent the risk of contamination, though it is likely that time pressure also contributed."

There were signs of trouble before the tests were sent to the public health labs, the review found.

Before they were shipped out, the test kits "began showing issues with negative controls showing positive results," the review said. However, the kits were not vetted in advance with standard quality control and quality assurance, or "QC/QA," procedures, according to the review.

"It appears that time pressure to ship test kits out quickly — and before QC had been conducted on them — might have compromised sufficient QC/QA to identify certain anomalies in data and realize the possibility of contamination before shipment," the review said.

Asked by e-mail if disciplinary action has been taken or is contemplated against any CDC employee involved with the test kits, an HHS spokeswoman declined to comment.

Present and former federal scientists experienced with infectious-disease testing and a congressman who has sought answers about what went wrong at the CDC said sending out the test kits without adequate quality control was indefensible.

"They should have waited," said Stephen Morse, a retired senior CDC microbiologist.

Rep. Raja Krishnamoorthi, D-Ill., who has praised coronavirus testing efforts in South Korea, Taiwan and other countries, said, "We have to look back at those weeks in February as having been the critical period in which the [U.S.] government's response totally failed."

The top HHS spokesman, Assistant Secretary for Public Affairs Michael Caputo, said in his statement that "we never had a backlog of tests in this country." In subsequent responses to the Post on Saturday, HHS touted "the Trump Administration's historic coronavirus response."

A separate audit of the CDC's handling of the test kits remains underway by the HHS Office of Inspector General and is not expected to be completed until 2021.