Brighton have launched an investigation after excrement was found on the floor of the Crystal Palace dressing room before Monday's Championship play-off second leg at the Amex Stadium.

The incident, an apparent attempt to unsettle the visitors when they arrived at the ground, prompted a furious email to staff from the Brighton manager, Gus Poyet, whose side lost the game 2-0.

Poyet, linked with moves to Fulham and Everton, was suspended by Brighton on Thursday over an unrelated alleged breach of contract, as was his assistant, Mauricio Taricco, and the first-team coach, Charlie Oatway. It is not suggested that any of the trio were involved in the dressing-room incident.

In an angry email to employees, reprinted in the Sun, Poyet wrote: "For some reason that is still not clear to me, someone during the day had access to the away dressing room and done [sic] something terrible, trying to upset everyone related to Palace. To say it in clear English, someone had a 'poo' all outside the toilets, over and around the toilets…

"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."

The Palace manager, Ian Holloway, writing in the Croydon Advertiser after their victory, made no direct reference to the incident, but did say: "I don't particularly like Brighton now after some of the comments that were aimed at me and the players when we got to the ground, and they deliberately sent the team coach the wrong way too. A couple of other things happened but I'm delighted we managed to put them in our favour."

Poyet's email also criticised the club's marketing ploy to create more noise inside the stadium by handing cardboard clappers to the home fans.

He added: "It was an extremely silly idea and the result was an annoying noise. I am not for one minute blaming the result of the game on this, but it added only negative vibes to the proceedings."

To compound a miserable week for Poyet, he also came under fire from the former Spain midfielder Vicente, who was released by Brighton after the match.

Vicente told The Argus: "He is the worst person I've come across in football. For me he is a selfish person, very egocentric. I say that because it's how I feel. I won't talk badly about my team-mates, because they have been fantastic with me. What I think is unacceptable is that the manager makes fun of his players. I've seen things here that I have never seen in my career."