Roads were closed and people advised to stay indoors yesterday following the outbreak of a large fire at a disused factory on Dalton Industrial Estate, near Thirsk.
The blaze broke out at around 2.30pm and was so intense that fire crews were unable to enter the building.
Firefighters using specialist equipment were still tackling the blaze until late in the evening, although no-one is thought to have been injured.
North Yorkshire Police were also called to assist with the incident and closed the A168, which runs past the industrial estate, in both directions due the amount of smoke.
Motorists were being diverted away from the area, with only local access for residents, while householders were told stay indoors and to keep all windows closed due to the smoke.
A spokesman for North Yorkshire Fire and Rescue Service said: "Due to the construction of the building and the intensity of the fire, officers have been unable to enter the property and it is anticipated that it will take a further number of hours to completely extinguish the fire."