The Americans had been taking part in military exercises in Australia.
A 21-year-old woman was allegedly attacked after a party in Western Australia on Friday. Police say detectives in Western Australian and the northern Australian port of Darwin questioned everyone who was at the party, including the servicemen, said police spokesman Rod Burke.
"We spoke to everyone who was present at the party," Burke said. "The majority were interviewed in Darwin because everyone has moved on and they are being transported back to Japan."
No charges have been filed in connection with the incident.
A U.S. Embassy spokeswoman in Canberra confirmed that some Americans had been questioned in connection with the incident. But she said the embassy hadn't been given any details about the alleged assault.
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