Fire crews in Kent have warned it is only a matter of time before somebody is badly injured or killed after a rise in woodland fires.
There have been more than 800 outdoor fires in the drought-hit county since the start of April, double the number for the same period last year.
The rise had led to serious concerns about the number of fires being started deliberately on Dartford Heath.
Kent Fire and Rescue said it had sent crews there 18 times since 1 April.
It said firefighters had found either grass, undergrowth, heathland or rubbish alight.
'Not harmless fun'
It said for most incidents, one fire engine was sent to the scene and the fire was dealt with quickly but some incidents had required two or three fire engines to bring blazes under control.
Dartford watch manager Lee Abel said: "The people responsible for these fires need to be very clear that arson is a crime and certainly not harmless fun.
"Deliberate fires are destructive and dangerous and have an impact both on the environment and the community in which we all live and work.
"Our aim is to educate youngsters about the dangers of starting fires but there is also a warning about the consequences for individuals caught committing arson, which can result in large fines or several years in jail - possibly a life sentence if someone is killed as a result of their actions."