"I can tell you the story is absolutely not true," spokesman Mark Adams said at the Olympic Park, after receiving a message on his mobile phone.
"It (the message) is from USOC (United States Olympic Committee). It's a false story."
Fox Sports News had reported the incident, and quoted the swimmer's mother as saying the incident had been "terrifying".
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USOC said it was finding out "truth and details".
(Reporting by Ossian Shine; Editing by Brian Homewood)
