The west London team launched an investigation after footage on social media showed a fan in the stadium's Shed End directing a racist gesture at Son during the 2-2 draw Sunday, promising the "strongest action from the club" if the supporter was identified.
And on Saturday, Chelsea made an official statement confirming they had "identified and banned a season ticket holder indefinitely" after their initial statement on the incident.
"Chelsea Football Club finds any form of discriminatory behaviour totally abhorrent," the first statement from the club read. "It has no place at Chelsea or in any of our communities.
"Chelsea FC has consistently made its zero tolerance position on discriminatory behaviour very clear, yet there are still idiots like this that attach themselves to this club as so called 'fans', which shames Chelsea FC, our coaches, players, staff and our true supporters."
In 2019, Chelsea issued a lifetime ban to a supporter who racially abused Raheem Sterling when he was playing for Manchester City in a Premier League match between the clubs, also handing temporary bans to five other fans in connection with the incident.
The same year, a Chelsea fan was arrested for alleged racist abuse toward Son in a game at the Tottenham Hotspur Stadium, while then-Chelsea centre-back Antonio Rudiger also reported being subjected to monkey chants during that match.