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The county's fire service says the youngest person it has had to work with to prevent them from setting fire to something was just three-years-old.
An intervention team which helps children who have either set light to something or shown an interest in doing so, say parents should know what to look out for.
It comes as recently-revealed data shows Medway is the worst area for deliberately-started fires and reports of arson made to the police.
Statistics from Kent Fire and Rescue (KFRS) – recorded between January 1 and May 11– shows 172 out of 689 deliberately-started fires were in the Medway Towns.
A Freedom of Information request revealed there were 253 fires started on purpose in Medway last year, followed by 163 in Swale.
Furthermore, separate police data shows there have been 68 reports of arson in Medway and 36 in Swale so far this year.
While the fire service record deliberately-started fires, this may not always mean a report of arson is made to the police.
Between January 2018 and this May, the force identified three cases in which the suspect was below the age of criminal responsibility, which is 10.
KFRS has a dedicated team called Firesetters which aims to help under 18s who have either set fire to something or shown an interest in doing so.
Referrals to the service can come from parents, guardians, or professional agencies such as social workers.
Team supervisor Anna Ryan said: "We'd rather speak to them before the act rather than after.
"It's all about prevention rather than cure."
She told the Local Democracy Reporting Service the reasons why children may turn to this behaviour is varied and can be due to a change in their emotional needs.
Children in infant school would be helped through using storybooks, toys, videos, and games.
She added: "A lot of the time when parents contact us, they think they're one of very few parents going through this particular issue but it is more common than people think, unfortunately."
Her tips for parents include making sure any fire-starting materials are kept out of reach, especially for younger children, and having a conversation with the child if lighters are found in their school bags or bedrooms.
Meanwhile, police data shows there were 619 reports of arson recorded across the county last year, with 108 of those occurring in Medway.
In most cases – 368 – while the investigation was completed, no suspect was identified. Charges resulted from only 20 reports.
Between 2018 and May 2022, there were 25 instances where the suspect was too ill to prosecute.