A frightening prank by children was putting lives at risk on the railway tracks in Lurgan in 1991.
The youngsters were placing a piece of concrete on the line for a speeding train to hit.
A spokesman for NIR said: “This is very dangerous. If the obstacle was large enough it could derail the train.
“Not only are the lives of these children at risk playing on the line in the first place but the lives of passengers could also be put at risk.”
Fears for the safety of the children were raised by Councillor Hugh Casey who said the problem was not new to the area.
The councillor explained the danger arose when a fence was broken down.
“It’s continually broken down and time and time again replaced by NIR,” he added. “They even put up a vandal proof fence but that too has been broken down allowing children to climb through onto the tracks.”
The NIR spokesman said: “But it’s not kids who are breaking it down. Adults have cut holes in the fence to have access to lands where they can exercise their dogs.”