Everton are helping police after two Brentford footballers claimed members of their family were racially abused.
Rico Henry and Ivan Toney posted about the incidents on Twitter, after the match at Goodison Park on Sunday 15 May.
Henry, who scored the winning goal in Brentford's 3-2 victory and is from Birmingham, called for the incident to be investigated.
He wrote on Twitter: "I never usually speak out on things that don't physically harm me or my family but to see my mom upset after being racially abused by a few Everton fans brought fire to my stomach!
"I will do anything for them & whatever it takes to get the small minority punished! This is not acceptable & must be investigated immediately."
After tweeting about the fireworks reportedly let off outside the Brentford team hotel, Toney added: "And for the man that racially abused my family Il [sic] do everything I can to get you the punishment you deserve!"
Everton responded to Toney's post with a tweet which read: "There is no place in football - or society - for racism. We are assisting Merseyside Police to ensure the individual is identified and dealt with appropriately."
Merseyside Police confirmed late on Sunday night that an investigation had been opened.
Detective Inspector Catherine Cox said: "No matter what football team you support, there is absolutely no place for hate anywhere in Merseyside under any circumstances.
"Merseyside Police has investigated and successfully prosecuted so-called fans for racial abuse inside football stadia, and offenders have been handed football banning orders along with a criminal record for their behaviour.
"We will support the victims in this case and work with Everton Football Club to find those responsible and bring them to justice. Their views and their abuse is not welcome here in Merseyside, and they do not represent the overwhelming majority of football fans.
"I would like to take this opportunity to encourage any football fans with information on racial abuse to speak with officers or stewards at the ground, or call 101 so we can identify and locate offenders, and ensure they face the consequences of their actions."