Six fire engines are currently at a building fire on Bawtry Road in Hatfield Woodhouse, Doncaster.
A large furniture storage building next to HMP Prison Lindholme, has been destroyed by fire.
The building is outside the Prisons boundary wall.
Fire crews from Thorne, Adwick, Doncaster, Rotherham, Barnsley and Epworth (Humberside Fire & Rescue) were called to the incident at 12:15pm on Thursday.
Firefighters have been tackling the blaze with hose reels and as at 2pm the fire is now under control and crews are damping down.
There are no reports of any casualties.
An investigation into the cause of the fire will take place once the fire is completely out.