England's Under-19 World Cup winner was visibly angry at the end of the Reds' 2-0 UEFA Youth League win at Prenton Park and had to be restrained by team-mates and coaching staff at the final whistle.
Liverpool confirmed they have "followed the proper procedure by reporting the alleged incident to UEFA" and Press Association Sport understands the incident is believed to relate to alleged racist abuse.
It is the second time this season Liverpool have been forced to act against the Russian club after Brewster's team-mate Bobby Adekanye was racially abused by fans during the game in Moscow in September.
Spartak were found guilty on that occasion and ordered to partially close their academy ground for one match.
Source : PA
Source: PA