Police say they are treating the fire which broke out in a portable building over the weekend as suspicious.
Two fire engines from the Lynn station were called to the building in Chapel Road, Pott Row, just before 7.10pm on Sunday.
Crews were on scene until 7.45pm after using hose reel jets and thermal imaging cameras to put out the fire.
No-one was reported to be injured in the fire but the building was extensively damaged.
Anyone with information should call police on the 101 number.