In a statement, the agency said that the PCR kits, which test for coronavirus infection, were made in China by BGI Genomics and that the errors were discovered during routine quality control checks in two laboratories. The tests were unable to distinguish the difference between very low levels of virus infection and a negative result.

According to the agency, the tests were used to conduct at-home tests between March and August. Approximately 3,700 residents received false positive results, the agency said.

“The two laboratories have analyzed samples from a total of ten regions in Sweden, of which nine have received incorrect test results. This applies to Stockholm, Västra Götaland, Gävleborg, Västerbotten, Västmanland, Dalarna, Västernorrland, Sörmland and Blekinge,” the agency said in a statement.

The agency also noted that a majority of the people that received the false positive test results “have had mild symptoms or have not felt any symptoms at the time of the test.”

“The incorrect test kit has been reported to the Medical Products Agency. It has been exported from China to many countries other than Sweden. The Swedish Public Health Agency has informed the corresponding authorities in Europe and the WHO of what happened,” the agency’s statement added.

Karin Tegmark Wisell, head of the agency’s microbiology department, said that “it is good that the error has been discovered and that the necessary measures have now been taken to ensure the quality of the test results.”

As of Wednesday, there were over 87,000 confirmed cases of the novel virus in Sweden and at least 5,817 deaths.

Newsweek was directed to the press release issued by Sweden’s Public Health Agency after reaching out for comment.

BGI Genomics, the company that supplied the tests, received emergency use authorization for its coronavirus testing from U.S. authorities in March and an Emergency Use Listing from the World Health Organization in May.

According to Reuters, two of BGI Genomics subsidiaries were recently placed on a U.S. economic blacklist by the U.S. Commerce Department. They were accused of human rights violations regarding China’s treatment of Uighurs in the northwestern region of Xinjiang.

After being placed on the blacklist, the company released a statement denying any allegations of human rights violations.

“BGI Group does not engage in unethical practices and does not provide gene technology for the surveillance of Uighurs. BGI Group does not condone and would never be involved in any human-rights abuses,” the statement said, according to Reuters.