The FA are looking to speak to Liverpool midfielder Harvey Elliott following Chelsea's Carabao Cup final defeat.
The Blues lost on 11-10 on penalties after a 0-0 draw which saw four goals ruled out for offside.
Chelsea goalkeeper Kepa Arrizabalaga missed the deciding spot-kick, handing the Reds the trophy.
Elliott came on as a second-half substitute but was initially not named in Liverpool's matchday squad.
An injury to Thiago in the warm-up meant the teenager had to be named as a substitute and came off the bench in the final 10 minutes.
As the Merseyside club were celebrating, Elliott was seen and pictured on the Wembley Stadium pitch holding a red flare.
The English FA have since been notified of the situation and will be seeking comment from the 18-year-old.
There has been no comment from manager Jurgen Klopp but the German could speak when he faces the media on Tuesday ahead of Liverpool's FA Cup tie 24 hours later.
