The Metropolitan Police has arrested a man after allegations of a confrontation with Sky Sports pundit Roy Keane at the Emirates Stadium on Sunday.
The 42-year-old man has been detained on suspicion of assault.
Both Keane and Richards have given statements to the Met.
The alleged incident took place after Arsenal triumphed 3-1 over Manchester United.
In an earlier statement the Metropolitan Police had said: "Police are investigating following an assault that is alleged to have occurred at the Emirates Stadium during an Arsenal v Manchester United match on Sunday 3 September.
Any witnesses or those with information are asked to call 101 ref CAD 6961/3 Sept.”