West Brom midfielder Jake Livermore jumped into the stands to confront a West Ham United fan who allegedly made a comment about the death of his baby son during their English Premier League match.
The supporter is understood to have shouted to Livermore, and the Hammers are investigating whether the abuse directed was about the player's baby, who died in 2014.
England international Livermore, who was substituted just after the hour, had to be escorted down the tunnel following the incident, which was not clearly picked up on CCTV footage.
West Ham acted quickly to eject the fan, who was spoken to by stadium staff on Tuesday evening, and are working with West Brom and the player himself to determine exactly what happened.
In a statement, West Ham said: "The player has today confirmed he does not wish to make this a police matter.
"However, given the nature of the allegations, the club will continue to investigate before taking the appropriate action."
The Football Association has also requested observations from all parties, which must be received by 6pm on Thursday.
West Brom issued a statement on Wednesday afternoon, offering the total support of everyone at the club to Livermore.
The statement read: "Following his substitution in the second half, Jake was subjected to general abuse from home supporters which he shrugged off.
"However, he acknowledges that he moved to confront one spectator who chose to make a comment about the death of his infant son.
"The club would like to think that all right-minded football supporters could understand this reaction which did not result in any physical exchanges before Jake was led away to our dressing room.
"Jake is an outstanding young individual who has the total support of everyone at the club and he has made it clear he considers this statement to be an end to an unhappy incident."