The HSE has said that up to 100 people have been given the wrong coronavirus test result and were in fact positive for the virus when told they tested negative.
A HSE statement issued to the Irish Mirror said: "The HSE identified that, on Saturday 11 of April, less than 100 people had been advised, in error, that their test did not detect Covid-19.
"On review these patients were, in fact, positive for Covid-19."
Chief Medical Officer Dr Holohan has vowed to personally investigate the error.
He has said: "It relates to a small number of people, it relates to tests that were processed in the laboratory in Germany and how those were designated.
"They are tests that would’ve been older, that in the ordinary course would’ve led to a second test, but at this interval it would be meaningless for the individuals involved."
The statement from the HSE said: "This error occurred because, in the case of a small number of lab tests, the initial test result was indeterminate.
"Ordinarily such results would indicate that another test is required.
"Given that we are dealing with a pandemic and that it was not possible to request another sample in the required timeframe, a decision was made to review the initial test results, and retest the sample."
The statement added: "This was done to maximise the chance of getting a test result for the patient if possible.
"The National Virus Reference Laboratory reviewed the detailed test data from the original test result and retested the original sample.
"As a result they were able to make a determination that some were, in fact, 'weakly positive'.
"Unfortunately, these indeterminate cases were initially reported as not detected and consequently were notified to people as such in line with the results communication process.
"This was picked up by our Contact Tracing Team and remedial action taken immediately."