Twelve fire engines were in attendance at a blaze near Crawley Down.
Crews were called to Rowfant Business Centre the early hours of Monday morning.
West Sussex Fire and Rescue Service was joined by colleagues from East Sussex, Surrey and Gatwick Fire and Rescue Services to control and minimise the spread of the inferno.
The conditions were made all the more difficult as the incident involved tankers of diesel and heating oil.
An investigation has been launched.