Chelsea beat Spurs 2-0 in the Premier League on Sunday, but the game in north London was marred by more than one allegation of racism from the stands.
The Metropolitan Police confirmed an arrest had been made after a member of the away fans was alleged to have committed "a racially aggravated public order offence" aimed at Son, per Sky Sports.
Chelsea released a statement on Monday, per the same report, detailing possible consequences:
"Chelsea Football Club will not tolerate any form of racism, nor is there a place at this club for anyone who is found to have engaged in such behaviour. If a season ticket holder or member is involved, we will take the strongest possible action against them including bans. We will also support any potential criminal proceedings by the relevant authorities."
The exact moment Son is suspected to have been targeted is unknown. Son was sent off after appearing to kick out at Chelsea's centre-back Antonio Rudiger two minutes after the hour mark.
Rudiger informed his captain Cesar Azpilicueta he had been the subject of racial abuse from somebody in the home crowd shortly after Son's dismissal.
Azpilicueta relayed the information to referee Anthony Taylor, who temporarily stopped play while announcements were made on the tannoy at Tottenham Hotspur Stadium that racist abuse was interfering with the game.
Spurs posted a statement on the club's official website on Monday, describing initial findings from an investigation into the incident as "inconclusive."
The statement also detailed the steps Tottenham are taking to investigate:
"We are able to track every fan via the cameras and have spent many hours reviewing CCTV footage. We have engaged lip readers to study the footage and contacted Chelsea for further information from their players. We have also taken statements from other parties present at the time. The police will be reviewing our evidence alongside us. Please be assured we shall be exhaustively investigating this matter."
Spurs also addressed the issue of protocols and if the right procedure was followed after Taylor had been alerted. There were three separate announcements in the stadium, even though UEFA protocols indicate a match can be abandoned after two warnings, according to BBC Sport.
However, Tottenham's statement identified how Taylor following UEFA directions about making announcements in-stadium "created a misconception that any issue was on-going."
Spurs also noted how Premier League procedures call for those identified engaging in abuse "be dealt with by the Safety Team in the first instance."
The Premier League responded to the confusion on Monday, per Dan Roan of BBC News:
Dan Roan @danroan
Premier League says it “will not tolerate discrimination in any form” after alleged racist abuse during Spurs v Chelsea y’day. Says it “uses a protocol specifically designed to support players, managers & officials who believe they are being subjected to discriminatory abuse” https://t.co/3CzyPK4S4J
Many, including Henry Winter of The Times, would like to see those governing English football's top flight do more to help tackle the problem:
Henry Winter @henrywinter
It might help the fight against racism in English football if @premierleague @FA @EFL @PFA contributed more than £779,000 between them to @kickitout annually. Kick It Out's vital work has never been more important to the game, so the game should give them more respect - and funds
Meanwhile, FIFA responded to an incident involving a player accused of engaging in racial abuse by handing a 10-match ban to Bahrain international Sayed Baqer, per Sky Sports.
The 25-year-old was also fined £23,600 after being found guilty of making a gesture toward fans during his nation's qualifier for the 2022 World Cup in Qatar against Hong Kong back in November.