The NI Health and Safety Executive has said it is in discussions with poultry giant Moy Park to understand the circumstances of the death of a worker.
The trade union Unite claimed the woman, in her 50s, had died after contracting Covid-19.
It called for the factory where she worked in Dungannon to be temporarily closed and all staff tested.
Moy Park said that significant safety measures had been in place for some time and were stringently followed.
Unite has written to the first and deputy first ministers demanding mass testing for agri-food workers and a special task force to oversee infection control in meat and poultry factories.
"Unite has now confirmed that a worker based in Moy Park Dungannon has died following contracting the Covid-19 virus," said regional officer Sean McKeever..
"This is devastating news and we would like to extend our condolences to her friends and family," he added.
The union called on the Health and Safety Executive for Northern Ireland to carry out site visits to Moy Park and other food production facilities to assess the effectiveness of disease control measures.
In an apparent change of tack, HSENI has confirmed it is now carrying out unannounced inspections to firms, with an emphasis on food processing companies and sites where there were repeated complaints.
"We can confirm that a recent unannounced inspection was carried out at a Moy Park meat processing plant.
"A few minor issues were found but the overall compliance with the PHA COVID-19 guidance was found to be of a high standard," it said in a statement.
In a statement Moy Park extended sympathy to the family of the worker who had died.
The company said it had put a number of measures in place including perspex screens, staggered breaks and enhanced cleaning.
"These measures have been in place for some time at all our sites and are stringently followed," the company said.
"These are also exactly the type of measures that government guidance is now calling for as other industries return to work."
Food companies have kept working throughout the coronavirus crisis, but there have been issues over reassuring staff that it was safe to continue.
In March, some staff at Moy Park's Portadown plant staged a short walk out over concerns about protection measures in place for workers.
Since then the executive has set up an advisory committee involving employers, trade unions, health experts and the HSENI to produce guidelines on safe working in factories and other facilities.
The guidance emphasises the need for social distancing and barrier methods of disease control where the 2m (6ft) rule cannot be adhered to.
Earlier the Unite union highlighted what it said were a growing number of Covid 19 clusters in meat plants and called for greater action from the executive.
It said Linden Foods in Dungannon had had seven positive cases and it was aware of issues in other meat plants.
Linden, which employs 1100 people in the town, confirmed that a number of staff had tested positive in recent weeks.
It has spent a six-figure sum on social distancing measures including Perspex screens and temperature checks on staff and has staggered start and meal break times in an attempt to stop the spread of the virus.
Omagh Meats also confirmed that it too had had a number of positive cases among workers following a story in the Tyrone Herald.
It said other workers were being tested and it was complying with protocols.
As key workers, agri-food staff are eligible for testing under the government's scheme, which is using specialist centres to try and increase the numbers of NHS staff and other essential sectors getting checked.