The force said it is investigating a video which appears to show youngsters deliberately trying to start a fire at Worden Park.
It comes as the county's fire service is already dealing with major wildfires at Darwen Moor and Longridge Fell, where 100 firefighters and around 20 engines are deployed.
But as Lancashire fire crews brave the raging forest and moorland fires, video has emerged reportedly showing teenagers setting fire to dry grass in the Leyland park.
Temp Ch Insp Chris Abbott, of Chorley Police, said: “We have been made aware of these videos and are taking the matter very seriously.
"The actions of these mindless idiots are reckless and irresponsible.
"We are working to identify those involved and will speak to them in due course."
"This is not a joke and the damage these fires cause can be immeasurable. We will be sharing these videos with Lancashire Police."