They also report that obscenities were written on the walls and sides of toilet walls in permanent marker pen, vile posters were stuck on the walls and the wash basins were wrecked in what has been described as a "pre-meditated" attack.
It is understood the changing area affected should only have been accessed by Leeds players and club staff during the semi-final second leg.
Someone had also badly damaged the changing room wash basins by kicking or hitting metal stands.
North End chief executive Steve Jackson said: "The lowest point in my footballing career was finding out about that. The posters were removed straight away and consigned to the bin but they were said to be "pre-planned".