Arsonists torched a trampoline in a St Helens park.
Firefighters were called to a park on Hard Lane shortly before 8.15pm last Wednesday (June 25) after the fire service control room received 10 999 calls within minutes.
The trampoline, which was set into the ground, measured around two metres by two metres.
It was left severely damaged by the flames.
Watch Manager Mike Costello, of Eccleston Fire Station, said: “There was quite a lot of black smoke being given off by this fire - we could see the smoke as we left the station.
“Fires such as these can pose a risk to those who may have started them and to nearby residents if their windows are open. It could also have posed a risk to passing traffic too if the smoke had blown across the road.”
Firefighters were at the scene until just after 9pm.