Chelsea defender Antonio Rudiger has urged Tottenham Hotspur to find and punish the individuals who allegedly directed racist abuse at him during Sunday's Premier League match.
The German was involved in an incident in which Tottenham's Son Heung-min was red-carded in the 62nd minute and indicated shortly afterwards that he had been the victim of a monkey gesture from the home section of the crowd.
Spurs have so far been unable to identify any home supporter making racist gestures but a Chelsea fan was arrested for allegedly racially abusing Son and was ejected from the ground.
Sky Sports reported on Monday that the Metropolitan Police had confirmed that the supporter was arrested after allegedly committing a racially aggravated public order offence. Chelsea said they were aware of the alleged incident involving a supporter and vowed to take action and also "support any potential criminal proceedings by the relevant authorities."
The Professional Footballers' Association (PFA) called for a government inquiry into racism in the English game following the match between the London rivals, which Chelsea won 2-0.
"I really hope that the offenders will be found and punished soon, and in such a modern football ground like the Tottenham Hotspur Stadium with dozens of TV and security cameras, it must be possible to find and punish them," Rudiger wrote on Twitter.
"If not, then there must have been witnesses in the stadium who saw and heard the incident. It's just such a shame that racism still exists in 2019. When will this nonsense stop?"
Tottenham are reviewing CCTV footage and vowed to take the "strongest possible action" if any supporter is identified as having made racist gestures but said in a statement their investigations so far have been inconclusive.
"We are able to track every fan via the cameras and have spent many hours reviewing CCTV footage," the club said. "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.
"Any fan found to be guilty will receive a lifetime ban. At this time, however, we should point out that our findings are inconclusive and would ask that comment is reserved until the facts are established."
The FA, the country's football governing body, is working with all parties to establish facts before taking action.
"Following the incident in the match between Tottenham Hotspur and Chelsea... we're working with the match officials, the clubs and the relevant authorities to fully establish the facts and take the appropriate steps," the FA said in a statement on Twitter.
The British Prime Minister's office issued a statement expressing support for the efforts to stamp out racism.
"Clearly there remains more work to be done by the football authorities in tackling this issue and we are committed to working with them on this to stamp it out," a spokesman said.
"The FA, Premier League and English Football League have significantly stepped up their efforts, but we expect them to continue to prioritise this issue and to consult with both players and supporter groups," the spokesman added.
"We will be monitoring how the football authorities implement their plans through the season. We will continue working with the authorities on this, including the PFA, and we don't rule out taking further steps if required."
The Premier League said it would not tolerate any forms of discrimination and that anyone found guilty of abusing Rudiger or Son deserved punishment.
Anti-racism organisation Kick It Out applauded referee Anthony Taylor for following the protocol which led to repeated stadium announcements warning the fans.
Rudiger is the latest Premier League player to suffer alleged racist abuse during a match, with Manchester United's Fred targeted by a Manchester City fan this month.
Racist incidents have tainted European football, with Inter Milan's Romelu Lukaku and Brescia's Mario Balotelli subjected to racist insults from rival fans during Serie A matches in Italy this season.
"It's really sad to see racism again at a football match, but I think it's important to talk about it in public. If not, it'll be forgotten again in a couple of days [as always]," Rudiger added.
"I don't want to involve Tottenham as an entire club into this situation as I know that just a couple of idiots were the offenders. I got a lot of supportive messages on social media from Spurs fans as well... thank you a lot for this."