Fire destroyed the Offaly plant of yoghurt company Glenisk on Monday, with director Gerard Cleary saying "basically everything" had been lost.
The alarm was raised shortly after 11am but the blaze spread quickly through the plant at Killeigh, outside Tullamore in Co Offaly.
Fifty staff working on site at the time were safely evacuated from the building.
In a statement on Twitter, the company said: “Devastated to confirm a serious fire at our plant today.
“All colleagues safely evacuated. We will assess the damage and move forward. Heartfelt thanks to the emergency services.”
Speaking to RTÉ, Mr Cleary said: “It’s devastating for all of us really at this point in time and we don’t really know what to say.
“Anything that gets us to get a pot of yogurt to the supermarket shelf, that’s all gone at the moment. But we’re resilient, we’ll fight back,” he added.
“We’ll just have to see what we have and what we can salvage and then just start again. That’s all we can do.”
Glenisk is the largest yoghurt maker in the State and says it accounts for 90 per cent of all the organic milk produced in the Republic and Northern Ireland.
That means the knock-on effects for the 50 or so farmers who supply the company will be sizeable until they can get back into production. Glenisk employs about 85 people at the plant.
Offaly Fire and Rescue said it had 34 firefighters tackling the blaze over the course of the afternoon, with units attending from Tullamore, Edenderry, Clara and Portarlington. Some staff were reportedly treated for smoke inhalation.
No cause of the blaze has yet been determined.
“We’re just grateful to all the services, the fire brigade and the ambulance,” Mr Cleary told RTÉ. “Luckily no one was injured in any way, so we’re very thankful for that.”