More than 40,000 people are understood to have been given a false negative Covid test, the UK Health Security has said.
NHS Test and Trace in England has suspended testing operations at the privately run Immensa Health Clinic lab in Wolverhampton.
Experts estimate around 43,000 people may have been given incorrect PCR test results. It is believed that many of these people previously tested positive for Covid on a lateral flow device.
The incorrect test results are said to have been given out between September 8 and October 12 and mostly affects the south west of England.
Officials say it is an isolated incident attributed to this one laboratory, and testing at the lab has now been suspended.
The NHS is now contacting people that could still be infectious and is urging them to take another test.
Close contacts who have Covid symptoms will also be advised to take another test in line with UK Government rules.
Dr Will Welfare, Public Health Incident Director at the UK Health Security Agency, said: “We have recently seen a rising number of positive LFD results subsequently testing negative on PCR.
“As a result of our investigation, we are working with NHS Test and Trace and the company to determine the laboratory technical issues which have led to inaccurate PCR results being issued to people.
“We have immediately suspended testing at this laboratory while we continue the investigation.
“There is no evidence of any faults with LFD or PCR test kits themselves and the public should remain confident in using them and in other laboratory services currently provided.
“If you get a positive LFD test, it’s important to make sure that you then get a follow up PCR test to confirm you have COVID-19. If you have symptoms of COVID-19, self-isolate and take a PCR test.”
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