Several tickets for next weekend's FA Cup final between Liverpool and West Ham have been stolen from a Royal Mail delivery van.
The match was due to be the inaugural game at Wembley
They were taken from the vehicle in Liverpool on Friday, Merseyside police say.
The stolen tickets have been cancelled and Merseyside police are warning fans not to buy match tickets from unauthorised sellers.
The match takes place at Cardiff's Millennium Stadium on Saturday.
A spokesman for Merseyside Police said: "Fans are advised, tickets stolen on 5 May from a Royal Mail van in Liverpool have been cancelled and will not be accepted for the game."
Merseyside Police said more details about the theft and the number of missing tickets was expected to be released on Monday.
Liverpool Football Club also issued a warning to fans not buy Cup Final tickets on the black market following the theft.
A club spokesman said: "We urge our supporters not to buy tickets from unauthorised sources as they run the risk of not being allowed into the Millennium Stadium and of being arrested for being in possession of stolen property.
"However, all tickets had been sent by special delivery so we will have an exact record of the individual seat numbers.
"We will be working over the weekend to identify the missing tickets."
The stadium holds 74,000 with Liverpool and West Ham allocated 24,436 tickets each for the game, with the rest going to the FA.
The match should have been the inaugural FA Cup final to be held at the new Wembley stadium - which will hold closer to 90,000, but it was not built on time.
It meant the number of tickets allocated to each club was reduced.
In a separate development in Liverpool, thieves have also stolen £80,000 worth of tickets for Take That and Girls Aloud pop concerts.
Police say four teenagers broke into the Radio City box office at the base of St John's Tower in the city centre.
Thousands of tickets with a value of up to £142 each were stolen.
Merseyside Police said the tickets have been cancelled by the ticketing agent, and the stolen tickets are now "worthless".
They warn anyone using them at an event will not gain entry and may face questioning about where they bought them.