The FA has described racist tweets directed at two footballers who missed penalties for England on Sunday as "appalling and unacceptable".
Police have launched an investigation into the racial abuse of Chelsea defender Ashley Cole and Manchester United winger Ashley Young .
They were singled out for abuse on the social network by one user, calling themselves Steve.
In a series of offensive postings the user goaded others who criticised him for his rants.
In one post the tweeter wrote: "All I got to say is this was just a joke, you guys need to relax, police know i was kiddin around and they won't bother me hopefully, cheers."
The most recent tweet says: "The police won't bother me mate i can assure you that."
The Football Association said in a statement: "We are concerned at the reports regarding allegations of abuse aimed at England players Ashley Cole and Ashley Young on Twitter.
"They have just given everything for the national team at Euro 2012 and it is appalling and unacceptable that messages of an abusive type are being posted."
The Metropolitan Police said: "We are aware of alleged racist comments on Twitter following last night's England game and have launched an investigation.
"The allegation was made to MPS on 25 June by a member of the public relating to comments on a Twitter account supposedly based in London.
"No arrests at this early stage.
"The MPS is examining possible offences under Section 18/19 Public Order Act 1986."
This is not the first case of footballers facing racist abuse on Twitter.
Liam Stacey, 21, from Wales was given a 56-day sentence in March for mocking Bolton footballer Fabrice Muamba after he collapsed on the pitch and also racially abusing two Twitter users.
One of his tweets read: "LOL. **** Muamba. He's dead!!! #Haha".
The Swansea University biology undergraduate was quickly tracked down and arrested
He admitted inciting racial hatred when he appeared at Swansea Magistrates' Court.