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Firefighters were called out twice yesterday to attend blazes believed to have been caused by youths.
The suspected arson on Dartford Heath at about 5pm prompted Kent Fire and Rescue Service to urge witnesses to come forwarded.
It followed a similar incident an hour before.
A fire service spokesman said: "Please help us by reporting fires immediately, rather than presuming someone else has already made the call.
"Give as much information as you can including location and nearby landmarks to help our crews respond quicker and reduce the risk of the fire spreading."
Crews used an all-terrain vehicle, fire fogging unit and beaters to extinguish the fire.