Drone footage showed the extent of a fire at a two-storey building on an industrial estate.
It broke out on Shire Hill, Saffron Walden, at about 14:38 GMT on Tuesday.
Six crews were sent to the building, which measures 8m (26ft) by 15m (49ft).
Essex County Fire & Rescue Service said firefighters remained on the scene overnight and into the morning to dampen down hotspots.
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