Vandals have caused an estimated £50,000 of damage to the train made famous by the Harry Potter films.
The number 5972 is well-known by Harry Potter fans
A gang of six youths are thought to be responsible for smashing about 200 windows on the Hogwarts Express, which is stored in Carnforth, Lancashire.
West Coast Railways (WCR), which operates the train, said hammers were used to smash the toughened glass.
Officers from British Transport Police (BTP) are investigating the incident, which happened on 10 March.
A spokeswoman told BBC News that 200 of the rolling stock's 230 windows were smashed during the wrecking spree.
Work on repairs is yet to get under way as officers, including forensic teams, are still examining the damage.
No timetable has yet been put on getting the train back up and running, the spokeswoman added.
The attack was not the first time the iconic train has been hit by vandals.
In September 2003, the company was forced to spend about £3,000 on repainting one carriage after it was daubed with graffiti near Scarborough, North Yorkshire.
The number 5972 - emblazoned on front of the engine - is instantly recognisable with fans of J K Rowling's books.
The train is used during the summer by tourists across the country and it is also hired out to Warner Bros for the Potter films