Carroll Cuisine in Tullamore, Co Offaly, has received confirmation from the Health Service Executive that tests carried out on 210 workers last Sunday are 100% negative.
The decision to suspend operations at Carroll Cuisine yesterday followed a spike in Covid-19 cases in the midlands, with three other meat plants already closed.
Following talks in Dublin yesterday, Meat Industry Ireland and SIPTU agreed that a wider level of Covid-19 testing is required at meat processing plants.
On Sunday, Carroll Cuisine had workers re-tested in cooperation with the HSE, after nine staff tested positive for coronavirus last week.
The company said it was a precautionary measure and workers were sent home on full pay pending the test results.
Chief Executive Kieran Carolan said the company was greatly relieved at the test results and that health and safety was a priority at all times.
Taoiseach Micheál Martin has said that weekly testing for Covid-19 will be rolled out at all meat plants and direct provision centres across the country.
Mr Martin was speaking after a meeting of the Cabinet sub-committee on the virus was briefed by senior health officials.
SIPTU's Divisional organiser, Greg Ennis, welcomed that announcement, and said the trade union has been "calling for this testing regime to be put in place for some time now".
He added that a quick turnaround time for test results is needed.