Samoans Alesana Tuilagi and Faifili Levave were also cited for foul play during the loss to Japan on Saturday and could miss their country's final Pool B match against Scotland.
Flanker Hooper was penalised for the clear-out of England fullback Mike Brown, which took place just before halftime in Saturday's Twickenham clash, but escaped further sanction from referee Romain Poite.
If found guilty of the offence of "charging into a ruck or maul without use of the arms or grasping the player", Hooper would miss Australia's Pool A decider against Wales on Saturday.
That would be a blow to the Wallabies, who have used Hooper and his fellow open side flanker David Pocock to great effect in victories over New Zealand, Fiji and England this season.
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Saturday's match back at Twickenham will decide which of the countries tops the pool, with the losers likely to face twice world champions South Africa in the quarter-finals.
Last weekend's showdown with the hosts, which resulted in England exiting a World Cup at the pool stage for the first time, featured some big hits from both teams.
England flyhalf Owen Farrell was shown a yellow card nine minutes from time for a dangerous tackle on Matt Giteau but Poite decided only to issue a warning to centre Sam Burgess for a neck-high tackle on Hooper in the same passage of play.
Rugby league convert Burgess was further sanctioned on Monday when he received a "citing commissioners warning" for the dangerous tackle.
Samoa captain Ofisa Treviranus received a similar warning for "striking an opponent" during his country's defeat to Japan on Saturday.
The warnings are the equivalent of an on-field yellow card but both players will be available for their country's final pool matches.
Treviranus's team mates Tuilagi and Levave were cited later on Monday, however, winger Tuilagi for "striking with the knee" and number eight Levave for playing an opponent without the ball.
Levave was shown a yellow card for the late shoulder charge, one of two sin-binnings for the Samoans in the first half of the 26-5 defeat to Japan.
(Reporting by Nick Mulvenney; editing by Sudipto Ganguly)
