At least 20 fire trucks have been sent to put out the blaze - which is being described as a "significant" fire, according to the Hereford and Worcester Fire Service.
Spokesman Richard Prine said: "20 fire engines heading to the Hoo Farm Industrial Estate in Kidderminster.He said the "first engine to arrive said the building was around 30% alight."
Locals have shared their concerns on social media, with one tweeting: "Been evacuated from work today due to this small fire."
Jon Laight, Hereford & Worcester Fire and Rescue Service Group Commander, described the fire as "significant".
In a statement on Twitter he said: "This is a significant fire so please avoid the area.
"For those in Kidderminster, keep your windows and door shut due to the large amounts of smoke being produced."
Firefighters are continuing to tackle the blaze and emergency services have confirmed there will be more updates throughout the day.
Roads heading into the industrial estate have been closed, with West Mercia Police asking motorists to avoid the area and seek alternative routes where possible.
The public is also being urged to refrain from visiting the area as well as closing windows and doors if they are near the plumes of smokes.
Kidderminster College has also closed its Vocational Skills Centre, although the main campus remains open as usual.
West Midlands Ambulance Service is also supporting fire crews.
They tweeted: "Due to the large amounts of smoke, all local residents are advised to keep doors and windows shut where possible."