Diouf is already being investigated by police over the allegation he racially abused a teenage ball boy.
The ball boy reported the alleged abuse, which appeared to take place after he threw the ball back to the controversial Senegalese international, to his superiors immediately after the game.
Police were informed and interviewed Diouf in the presence of a Blackburn official before the player left Goodison Park.
Diouf has since denied the allegations and has even hit back by claiming Everton fans threw bananas at him.
He told Radio Monte Carlo: "The ball went out and I wanted to take the throw-in quickly. The ball-boy threw the ball at me like a bone to a dog. The assistant referee told me he saw it but we had to continue and we would look at it at half-time.
"What's more, people threw bananas at me. The fourth offical said he would make a report to the police. I didn't say anything so that people couldn't say 'it's El-Hadji Diouf again'. I've had problems before but never like on Sunday."
A police officer and a member of Everton's groundstaff went to investigate the section of the pitch where Diouf claims fans threw bananas after the match, but found nothing.
An Everton spokesman said: "We really can't say much because the police investigation is ongoing.
"However, the only investigation being undertaken is into the allegations against El-Hadji Diouf. There is no investigation ongoing into the behaviour of Everton supporters."