Championship clash with Bolton Wanderers last month.
Sordell tweeted after the game “It’s 2012 in England and people are still shouting racial abuse at a football game!? #shocking.”
The Bolton striker also indicated that team-mates Darren Pratley, Benik Afobe and Lee Chung-Yong were also victim to discriminatory language from some Millwall fans.
The south London club have now released a formal statement concluding the investigation which was carried out in conjunction with the Metropolitan Police, Bolton Wanderers and the F.A.
“Having completed our investigations into the incident, we have identified and interviewed a 13-year-old boy who admitted a verbal exchange with Marvin Sordell in which abuse was used,” the statement reads.
The teenager has been banned from future matches at the New Den, but Millwall believe education over punishment should be the priority considering the boy’s young age.
“The individual has been banned from Millwall matches for the foreseeable future, but as a club we also felt, given the boy’s age and background, we had a duty to play our part in attempting to educate and rehabilitate him.
“Accordingly, we have offered to put him through one of our education programmes, run by Millwall for All (formerly the Millwall Anti-Racism Trust) in the hope that we can change his outlook on equality, racism and life in general.
“In the meantime, the boy has written a letter to Marvin Sordell offering his apology, which has been accepted.”
The statement also criticised sections of the media who misreported the incident claiming that racist chanting could be heard from large sections of the Millwall support.
“These reports were made with no knowledge of the facts and created the impression that Bolton players were subjected to racial chanting or systematic abuse by more than one individual.”
“Finally, it is our hope that all of us within football, including governing bodies, clubs, players, fans and the media can continue to work together to build on the progress that has been made over many years in effectively tackling the issue of racism in our game, rather than merely sensationalising, and thereby trivialising it,” the statement concluded.