A food factory in Co Kildare has suspended all operations after it identified 80 confirmed cases of the coronavirus.
O’Brien Fine Foods in Timahoe also said there appears to be a "very high" level of asymptomatic infection.
The company said an employee presented with symptoms in recent days.
In line with procedures, the factory immediately isolated the individual and a test was carried out.
Results received on July 30th confirmed that the person had tested positive for COVID-19 which, at that time, was its third confirmed case.
In a statement, O’Brien Fine Foods said: "We initiated engagement with the Health Service Executive (HSE) and took what we believe was the most responsible decision to test all employees which was coordinated by the HSE and a private provider to expediate testing."
Of 243 tests completed, 80 have been confirmed as positive for COVID-19.
Of the 80 confirmed, the company said the level of asymptomatic infectivity "appears to be very high".
A further 42 employees are still completing tests.
Those who have tested positive have been advised to isolate as per official guidance, and full risk assessment and contract tracing is underway.
While all close contacts of those affected are being notified, advised to self-isolate and to contact their GP.
The company added that it has operated a "rigorous" health and safety policy since February.
This includes working from home for all non-operations staff, mandatory PPE, Perspex screens, staggered shift and break times, restricted visitor to site policy and daily temperature checking.
"Given this level of rigour and our comparatively low level of confirmed cases up to this point, this sudden spike is difficult to comprehend", the company statement added.
It comes as 226 cases have arisen in Kildare, Laois and Offaly over the past 14 days.
People there are being urged to take immediate action if they have any COVID-19 symptoms, and double down on their efforts.
Those aged over-70 in in the three counties are also being warned to take particular care and limit the number of people they are in contact with.