Eight men have been arrested after an investigation into the online racist abuse of an unnamed Tottenham player.
Four other men were interviewed under caution as part of the Met police's investigation into the use of words or behaviour, or displaying written material with intent to stir up racial hatred.
The police launched the investigation after a Spurs player was racially abused online following the team's 3-1 loss to Manchester United in April.
Man United's own online reporting tool spotted abuse before the police in Manchester were made aware.
Detective Sergeant Matt Simpson from the Met's public order crime team said: "This action makes it abundantly clear that police will not stand for racist thuggery, even if it is committed online.
"The posts, all of which were on Twitter, were vulgar and were utterly unacceptable. There is no safe haven for this type of abusive behaviour, and we are committed to taking decisive action to root it out.
"With a busy summer of football approaching we are committed to driving out this type of racist behaviour - it has no place in football.
"I am delighted with the support we have received from our policing colleagues nationally and from Manchester United and Tottenham. Without them, it would be difficult to identify these users and take action."
