FIFA says its disciplinary panel is "analyzing incidents that occurred after" Canada's 4-3 defeat following extra time on Monday.
Canadian forward Christine Sinclair, who scored all three goals, later said "the ref decided the result before the game started."
A spokesman for the Canadian Soccer Association says the team will not comment on the investigation until FIFA makes a decision.
Canada was upset by an indirect free kick awarded against goalkeeper Erin McLeod for holding the ball too long late in normal time.
The resulting passage of play saw the Americans get a penalty which Abby Wambach scored to equalize at 3-3.
Despite their anger, the Canadians don't intend to protest the result. They play France for the bronze medal Thursday.
Wambach says she counted out loud when McLeod held the ball.
Canadian coach John Herdman said Wambach's comments demonstate her desire to win.
"She knows how to win football matches," said Herdman. "At the end of the day, this is why teams go on and win. They find ways to win. If Abby's done that, then good on her. She's found a way to find a loophole in the system that might punish a team. ... She'll do anything to win a football match."
Herdman said his players can learn from Wambach's actions. But Canada has enough to think about during games.
"I certainly won't be asking my players to go and do that," said Herdman. "I think they'll just go and play football as long as the referees officiate games, which is their job to do."
Herdman said his deeply disappointed players have to pick themselves up again and set their sights on getting on the podium.
"These next days are going to be crucial," said Herdman. "We can just minimize distractions and be ready to get absolutely clear about achieving the task and making the country proud by seeing that flag rise."
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