A warning has been issued by the Northern Ireland Fire and Rescue service after two boys had to be rescued from the 50ft crane in Coleraine, County Londonderry.
The boys were aged 14-years and 16-years.
Group Commander Max Joyce said a total of 24 firefighters were involved in the operation to bring the youths to safety at Pates Lane on Monday evening.
A specialist rescue team and an aerial ladder platform was deployed.
The rescue began at 8.35pm and the boys were handed over to police officers two hours later.
Mr Joyce told BBC Radio Ulster: “Our main concern was the youths at the top so we had to ensure that they were safe all the way through.”
He said firefighters managed to rescue the boys by placing them into the cage of the aerial platform, but he said he did not know why they were at the top of the crane.
“I would use this opportunity to appeal to young people not to be climbing up onto cranes,” Mr Joyce added.
“It would be very easy for someone to slip and fall. It’s not a playground, so don’t be doing that.”