Police are appealing for information following a series of arsons in Welwyn Garden City.
The first fire was set on the fence of the cricket club at King George V Playing Fields in Beehive Lane last month.
Police were called to reports of a fire at 8.04pm on Sunday, June 16 at the club and assisted the fire service at the scene.
The fire, which is being treated as an arson, also spread to a tree.
Since then the police have attended a series of other fires at the same location, which they are also treating as arson.
According to police, off-cuts of tree branches, a bin, an old bike and an old scooter have been set alight over the last couple of weeks.
Sergeant Ian Smith, from the Welwyn Hatfield North Safer Neighbourhood Team, said: "Thankfully nobody has been injured but this thoughtless behaviour could have had serious or even fatal consequences."
"We take a strong stance against anti-social behaviour and will not tolerate this.
"We have identified those involved - a group of young people, and appropriate action will be taken with our partner agencies.
"In response to these incidents, my team are regularly patrolling the playing fields and I would urge any witnesses or anyone with information to get in touch with us on the non-emergency number 101.
"I would also urge parents to be aware of their children's whereabouts at all times.
"If you know that your child is committing anti-social behaviour, we would suggest considering placing certain conditions on them such as curfews."
To report information online go to: herts.police.uk/Report.
Or speak to an operator at the Force Communications Room via an online chat at: herts.police.uk/contact.
Alternatively, you can stay 100 per cent anonymous by contacting the independent charity Crimestoppers on 0800 555 111 or via their untraceable online form at www.crimestoppers-uk.org.
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