A pork processor is closing for mass testing of its 500 staff after a "significant" outbreak in which 35 workers tested positive for Covid-19.
Cranswick plc in Ballymena said it had also temporarily suspended its exports to China in light of the positive tests.
The number of staff affected was confirmed by Health Minister Robin Swann, although it had not been revealed by the company.
He added that there had been a "smaller" number of positive cases among contacts of affected staff.
It is the first major factory here to shut down completely to deal with an outbreak.
Cranswick said it is requiring staff who have tested negative to self-isolate for 14 days - which is likely to mean that the factory will be shut for 14 days. It is to close from tomorrow.
Yesterday Mr Swann said: "As of yesterday evening there had been 35 cases identified within staff and a further smaller number of positive cases with contacts.
"Supported by the advice of the Public Health Agency and Chief Medical Officer, the outbreak is so significant and so extensive that all the workers in the factory and all recent visitors should now be required to self-isolate.
"This will see the plant closure of the factory and as a priority all staff will be tested and the plant will undergo a full deep clean over the period of the closure."
Trade union Unite said it is seeking reassurance that sent-home staff will not lose pay.
Unite regional officer Liam Gallagher said the meat processing sector had been badly hit in the pandemic.
"This latest outbreak in Cranswick shows that the issues in the sector have still not been addressed, despite the risks being highlighted since May," he said.
"In particular, Unite has consistently called for a significant increase in unannounced inspections by the HSE, along with other transparent and robust enforcement measures."
But the Health Minister said the outbreak "was by no means unique" to Cranswick.
"There have been outbreaks in similar facilities in England, Scotland and Wales and the Republic of Ireland," he said.
A spokesman for Cranswick said: "There has been a recent increase in the number of confirmed Covid-19 cases in Ballymena and the wider region and this has been acknowledged as a community issue.
"As a result of this, we can confirm that a number of colleagues at our Ballymena site have tested positive for Covid-19.
"Working with the Public Health Authority (PHA), we have taken the decision to send all of our colleagues for testing.
"If the test results are positive, the individual will be required to self-isolate for 10 days; if the test results are negative, the individual will be required to self-isolate for 14 days. Therefore, the site will need to temporarily suspend production.
"The health and safety of all of our colleagues has always been our number one priority and we have done everything we can to protect our Ballymena team."
The company said it had taken measures at the outset of the pandemic to protect staff, including social distancing measures, personal protective equipment (PPE) for all staff and additional cleaning and hygiene measures across the site. North Antrim DUP MP Ian Paisley said he was concerned about the impact of the closure on the agri-food industry.
He said the company had behaved responsibly but added: "We cannot have a situation where Covid prevents factory production that ultimately damages the Northern Ireland agri-food sector. That would be catastrophic."
Separately, in Mid-Ulster, well-known Magherafelt bar Dorman's said it is closing for the weekend after three members of the public who visited last weekend later tested positive for the virus. It is shutting for a deep clean to be carried out as well as testing of staff.
In an online statement posted on Facebook, Dorman's Bar said: "We are absolutely devastated that this has happened but unfortunately it is a situation that is unavoidable and which a lot of businesses will face in the coming months."
Belfast nightclub Thompson's Garage also remained closed yesterday evening after a staff member tested positive for Covid-19.
A spokesperson said all remaining staff members have been tested. "These results should be in today or tomorrow at the latest but sadly we cannot open until we are certain that everyone employed at Thompson's is in the clear," they said.
"In the interim the entire venue is undergoing a deep clean, fumigation and decontamination in preparation for reopening this weekend."