The Health and Safety Executive has begun visiting workplaces after receiving complaints about almost 500 employers during the coronavirus lockdown.
The organisation faced criticism after admitting it was not in a position to visit workplaces to inspect measures in place to prevent spread of the coronavirus. Instead it was contacting employers over the phone to discuss complaints and requesting evidence from them.
The Executive said those firms not enforcing stringent health measures faced "tough action".
In April it revealed it had a surge of complaints with a 1,800% increase in reports. It said the majority of the allegations concerned Covid-19 and social distancing measures in the workplace.
Workers have staged walkouts from factories over concerns for their safety and trade union Unite called for mass testing across the poultry and meat sector after the death of a Moy Park worker.
There is no suggestion that the firm was at fault and it said “robust” measures have been put in place to keep workers safe.
The BBC has revealed the Health and Safety Executive has received complaints about 480 companies between March 16 and May 4. It did not say how many individual complaints that included.
The organisation said the number of calls had decreased but was still "high and constant".
It said since May 4, it had been carrying out unannounced site visits with 36 undertaken so far.
The BBC reported inspectors had focused on those premises where had been multiple complaints, including some food production sites.
The Belfast Telegraph contacted the Health and Safety Executive, but has yet to receive a response.