Brighton have launched an investigation after excrement was found on the floor of the Crystal Palace dressing room prior to Monday's npower Championship play-off clash at the Amex Stadium.
Club sources confirmed the incident on Saturday, reported by The Sun, had occurred.
It sparked a furious email to club staff from Brighton manager Gus Poyet, whose side lost the home leg of the semi-final tie 2-0 to miss out on a shot at promotion at Wembley.
Poyet was suspended by Brighton on Thursday along with assistant manager Mauricio Taricco and first-team coach Charlie Oatway, however it is understood the club are not pointing the finger for the dressing-room incident at any of the trio, and have an open mind as to who was responsible.
Poyet's email to employees, reported in The Sun, said: "I am angry that someone within this club could endanger our good reputation and stoop so low.
"Did they imagine that this would affect the Crystal Palace players? Well possibly it did. It may just have fired them up more.
"Well someone made a very bad decision and I think it is time to stand up and take responsibility. Not just the culprit but those employees who are supposed to make our stadium safe and secure."