Raheem Sterling could face a ban after appearing to throw a missile back into the crowd during Chelsea's chaotic Premier League clash with Tottenham on Monday.
The incident occurred moments after Cole Palmer had brought the Blues level from the penalty spot in the first half following Cristian Romero's red card for an ugly lunge on Enzo Fernandez.
Palmer celebrated by putting his finger to his lips in front of the Spurs fans, and was congratulated by several of his team-mates, including Sterling.
A video from pitchside - which originated on Chelsea's own TikTok account - shows an object, launched from the area housing Tottenham fans, striking Palmer on the leg.
As the players break away to make their way back for the restart, Sterling appears to bend down and throw the item back into the crowd before running back to his own half.
The incident was not spotted by the officials at the time, but an FA source has told Mail Sport that it is being reviewed, as they look to determine whether any action needs to be taken.
Sterling went on to help Chelsea to a 4-1 win over their London rivals as Spurs were reduced to nine men in the second half when Destiny Udogie was shown a second yellow card.
The ill-tempered derby finished with Nicolas Jackson scoring a second-half hat-trick, and Sterling set up the first of his goals as he unselfishly squared the ball for a simple tap-in.
There have been a couple of other incidents of players throwing objects back into crowds in recent seasons.
Richarlison was banned by the FA for throwing a lit flare back into the crowd after scoring for Everton against Chelsea in May 2022, prior to his move to Tottenham later that summer. His one match suspension delayed his debut for Spurs.
Chelsea icon Didier Drogba was handed a three-match ban in 2008, when throwing a coin at Burnley fans during their Carabao Cup defeat on penalties.
And former Liverpool defender Jamie Carragher was also handed a three-match ban - and given a formal police warning - after hurling a £1 coin at Arsenal fans in an FA Cup clash at Highbury in 2002.