Manchester City suffered further misery following their shock FA Cup exit at the hands of Sheffield United at Bramall Lane.
South Yorkshire Police, with the co-operation of both clubs, are investigating the theft of a significant amount of money stolen from the City dressing room.
A United spokesperson confirmed: 'At some stage during the course of the afternoon, and not necessarily during the course of the 90 minutes, a theft took place.
'The theft involved money stolen from wallets - and not the wallets themselves - in the City dressing room, believed to be an amount between £1500 and £2000.
'South Yorkshire Police, Sheffield United and Manchester City are working together to investigate this matter.'
Premier League City were beaten 2-1 by Coca-Cola Championship side United at the fourth-round stage.
Luton Shelton and Jon Stead scored for the Blades in the first half, and although teenage star Daniel Sturridge pulled one back for City early in the second half, manager Sven-Goran Eriksson's side were unable to force a replay.
'A number of staff and players have had a quantity of cash stolen,' City spokesman Paul Tyrrell told Sky Sports News.
'I am not aware that the dressing room was locked and the police are looking in it.'