A jet on a flight from Paris to North Carolina was diverted over security fears after a French passenger handed a note to a flight attendant saying she had a surgically-implanted device.
An examination by doctors aboard the US Airways plane found that the passenger, a French citizen born in Cameroon, had no scars, an official said.
The woman was travelling alone without any checked baggage and intended to stay in the US for 10 days.
The FBI and Homeland Security Department warned airlines last summer that terrorists were considering hiding bombs inside humans to evade airport security.
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The Islamic centre where the Manchester suicide bomber is thought to have prayed says the attack "has no place in Islam or any religion".
German chancellor Angela Merkel and Indian prime minister Narendra Modi among those to praise "great spirit" of Manchester people.
The bomber's identity has been confirmed by Greater Manchester Police.