Youths are thought to be dealing drugs on the tracks at a scenic railway line.
Police have revealed they have found drugs paraphernalia alongside the tracks at Kirklees Light Railway.
It is thought they have been dealing bags of cannabis.
The intruders have also been starting fires and leaving empty cans of cider and lager.
The scenic route runs from Clayton West to Shelley Woodhouse.
A spokeswoman for Kirklees Rural Neighbourhood Policing Team said: “Nuisance youths on the tracks again at the Skelmanthorpe side of Kirklees Light Railway.”
And in a direct message to the troublemakers, she said: “Not only are you ruining someone’s day out, it’s dangerous and you’re trespassing. Any youths caught on the tracks will be dealt with for anti-social behaviour so please stay away.”
Kirklees Light Railway was opened on October 19, 1991 but the foundations of the line date back to the mid 19th century.
The railway, established by Brian & Doreen Taylor who had set up a miniature railway at Shibden Park in Halifax, was acquired in 2006 by Stately Albion, a family owned company that specialises in the manufacture of park and leisure homes. With six locomotives, 12 coaches, a new engine shed and station building at Clayton West the Taylors had laid solid foundations.
Since purchasing the line Stately Albion have made many improvements and these include new carriages, two large play areas and a new tearoom and picnic area at Shelley.