"Worrying" images of children sitting on a railway line used by trains travelling at speeds of up to 125mph (200kmh) have been released.
Network Rail published the CCTV pictures after it took the decision to temporarily close a level crossing in Rossington amid safety fears.
In one image a person can be seen lying down on the crossing near Doncaster.
Vicki Beadle, community safety manager at Network Rail said: "The railway is not a playground".
The crossing will be closed until 8 October with people being directed to a nearby footbridge.
Vicki Beadle, community safety manager at Network Rail, said: "The photos are deeply worrying.
"This crossing lies on the East Coast Main Line and sees almost 200 trains a day pass over it, which can travel at speeds of up to 125mph.
"As well as the high frequency and speeds of the trains, the crossing also has overhead line equipment, which carries 25,000 volts of electricity and would deliver a powerful electric shock to anyone coming into contact with the wires.
"The railway is not a playground and it's vital that users treat crossings with the respect they deserve."