A 16-year-old boy suffered serious burns when he fell from a railway platform on to a 750-volt live rail.
The teenager was with friends when he fell backwards on to the tracks at Swaythling station in Southampton on Tuesday evening.
He was taken to hospital in Southampton before later being transferred to a specialist burns hospital in Salisbury.
British Transport Police said it was treating the incident as an accident and not suspicious.
BTP Inspector Mick Morriss said: "This young man suffered serious burns as a result of this incident, which is an important reminder of the need to take care when near railway lines.
"The live third rail, which powers trains across the South, carries 750 volts of electricity and remains switched on 24 hours a day, seven days a week.
"The summer holidays are a well-deserved break for young people and we don't want them to end on a sad note."