Youths have been spotted in the cabs of heavy machinery in two separate incidents.
Inspector Nigel Storey said: “Children and young people need to remember that building sites are fenced off for a reason, for example bricks and pipes might fall on them or they might fall into something containing hazardous chemicals.
“The site machinery may resemble something they played with as a child but in inexperienced hands the machinery can be unpredictable and dangerous.”