Thousands of people received a wrong test result after being tested for the coronavirus in Sweden, health authorities said at a press conference on Tuesday.
All 3,700 people who got tested received a positive result although they were not infected with the coronavirus, impacting Sweden's official caseload statistics.
The wrong results concern especially people with mild symptoms who tested themselves using so-called PCR tests.
The fault was discovered in two laboratories who analysed the effectiveness of the PCR tests manufactured in China, finding that the tests could not distinguish between samples with a low virus concentration and negative samples.
The tests were simply not effective enough, health authorities said.
Sweden had by Tuesday recorded a total of about 86,900 coronavirus cases and 5,814 deaths from Covid-19.