London police launched an investigation Monday into the racial abuse of two of England's black football stars by an unidentified Twitter user after they missed penalty kicks at Euro 2012.

Chelsea defender Ashley Cole and Manchester United winger Ashley Young were singled out for abuse by one user, going by the name Steve.

In a series of offensive postings, the user goaded others who criticized 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."

Cole and Young both missed from the spot in Sunday's defeat to Italy on penalties in the Euro 2012 quarterfinals.

"We are aware of alleged racist comments on Twitter following last night's England game and have launched an investigation," Metropolitan police said in a statement.

"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."

In March, 21-year-old Liam Stacey, of Wales, was given a 56-day sentence for mocking Bolton's Fabrice Muamba after he collapsed on the field.

One of his tweets read: "LOL. **** Muamba. He's dead!!! #Haha." Stacey later directed racial abuse at other Twitter users.

The Swansea University biology undergraduate was quickly tracked down and arrested. He admitted inciting racial hatred when he appeared in court.