80 cases of Covid-19 have been confirmed at O'Brien Fine Foods in Co Kildare.
All operations at the company's plant in Timahoe near Naas ceased last night.
243 tests have been carried out among workers with 80 testing positive - while results for 42 employees are still pending.
In a statement, O'Brien Fine Foods said an employee presented with Covid-19 symptoms last week and was isolated immediately and tested.
Following the return of a positive test, the company consulted the Health Service Executive (HSE) and initiated company-wide testing.
All employees were tested and O'Brien Fine Foods reported a very high level of asymptomatic infectivity.
O'Brien Fine Foods said extensive Covid-19 health and safety measures had been introduced including guidance communications in multiple languages.
The company said it was fully audited by health inspectors prior to the Covid-19 cluster forming.
"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 statement said.
The warehouse facility is operating with minimum staff while deep cleaning is taking place.
The Labour Party has called for urgent action to protect workers in meat factories in Ireland.
Duncan Smith, TD for Dublin Fingal said: "The outbreak of a second wave of clusters in meat factories highlights how meat factories remain very dangerous for workers."
Earlier this evening the Acting Chief Medical Officer Dr Ronan Glynn urged people living in Kildare, Offaly and Laois to be extra observant of Covid-19 public health guidelines.
Dr Glynn also advised members of the public over the age of 70 living in those three counties to start limiting their contacts.
A further 69 Covid-19 cases were confirmed in Ireland today bringing the total number of cases since the outbreak began to 26,372.
Of the 69 new cases, 22 cases were located in Offaly, 19 in Kildare and eight in Laois.
There were five further deaths confirmed however four of these deaths date from May and June.