North Wales Fire and Rescue Service say they are dealing with a fire on the Deeside Industrial Estate.
A spokesperson said crews were called to the incident in a building on 4th Avenue, Deeside Industrial Estate, at 12.58pm.
Eyewitnesses have described hearing loud bangs from the Ifor Williams Trailers factory. They say there were large clouds of thick black smoke, but that the fire is now largely under control.
Appliances from Deeside, Buckley, Mold, Holywell, Wrexham and St Asaph, as well as the Aerial Ladder Platform, the Environmental Protection Unit and the Incident Command Unit, were all sent to deal with the fire.