Arsonists set a park bench and table alight in Park Avenue, Wisbech on Sunday evening.
Firefighters, who were called at 7.20pm, used a hose reel to extinguish the fire.
They returned to their station by 7.44pm.
A Cambs Fire spokesman said: “The cause of the fire was deliberate.”
Anyone with information should contact police on 101 or Crimestoppers on 0800 555111.
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