The first and deputy first ministers have told employers they must have social distancing measures in place.
That is the rule that employees must be kept at least two metres apart.
Arlene Foster said firms cannot carry on as normal and if they don't "get their act together", they will face enforcement action.
Earlier, staff at poultry firm Moy Park left their stations at its Portadown processing plant, claiming that social distancing was not being adhered to.
Moy Park said it has put new "robust" measures in place to protect staff, including staggered breaks and screens on some production lines.
Speaking at the Stormont Executive's daily update on the Covid-19 pandemic, Mrs Foster said food production sites were essential services, but employers must ensure staff safety.
The message on safety was echoed by Deputy First Minister Michelle O'Neill.
"Workers need to be protected," she said.
"We can't on one hand ask people to stay at home and follow advice and ignore it for those who are out at work.
"I have seen multiple men in a van going to work. That's not acceptable."
Staff walked out of food firm Moy Park over coronavirus safety concerns, a union has said.
Unite said workers left their stations because social-distancing measures had not been enforced at the Seagoe site.
A Moy Park spokesperson said they had already put "new, robust measures in place" to keep their employees safe.
They included staggering breaks, respacing workstations and communal areas and installing screens on some production lines.
"We are continually reviewing the situation and taking additional steps where necessary," the company said.
Over the past 24 hours, manufacturing workers from a range of companies have contacted the BBC raising concerns.
They said there were issues over social distancing - keeping more than 2m (6.5ft) apart from others.
In addition to the situation at Moy Park, 80 employees at ABP Food Group have left their stations at the firm's Lurgan site.
The Department of Communities has also come under fire for not putting in place social-distancing measures for its staff.
Deputy First Minister Michelle O'Neill said employers would be "called out for exploiting their workforce" if they do not follow the rules around social distancing in the workplace.
In other developments on Wednesday:
- A new assessment centre opened in Londonderry
- Two patients at a care home in Belfast tested positive for coronavirus
- Ulster University students were released from accommodation contracts
- The family of a care home resident who died with coronavirus said she was much loved
- A pastor who was severely affected by the virus made a plea from his hospital bed
- An appeal was made for retired GPs who want to help