South Korea midfielder Lee Chung-yong was among a group of Bolton players racially abused by Millwall fans during Saturday's Championship clash at The Den, according to Wanderers striker Marvin Sordell.
Sordell claimed that he, Lee, Darren Pratley and Benik Afobe had to endure racist taunts from Millwall supporters during Bolton's 2-1 defeat in south-east London.
The 21-year-old said on Twitter that he had reported the incident and revealed that he also received abusive responses to his allegations on the micro-blogging website.
England Under-21 international Sordell was an unused substitute, while Lee, Pratley and Afobe all came off the bench in the second half.
"Putting the match aside, its 2012 in england and people are still shouting racial abuse at a football game!? Shocking," Sordell wrote on Twitter.
"Chungy, Pratts, Benik and i had all sorts of things said to us. The police were standing yards away and did nothing.
"Funniest thing is if had come on and scored and gave them some back, i would be the one who got fined."
The Football Association confirmed they would investigate the incident and Millwall later released a statement, saying: "Millwall and Bolton Wanderers are investigating allegations made by Bolton player Marvin Sordell that he was subjected to racial abuse by an individual whilst warming up as a substitute during Saturday's Championship clash at The Den.
"The two clubs remain determined to do everything in their power to ensure that racist behaviour will not be tolerated.
"We will be speaking to the police and the match officials on this matter but no further comment will be made until this process has been completed and the investigations have been concluded."