TOKYO -- Japanese airport police have found 30 bullets in an American Airlines crewmember's carry-on bag and say the flight attendant apparently carried them through his security checks at U.S. airports.

Police at Tokyo's Narita airport seized the bullets after finding them Saturday during a security check before the man boarded his duty flight back to the U.S.

Airport police official Masatoshi Ito said Wednesday the crewmember - identified only as a male U.S. citizen in his 50s - told police he forgot to leave the bullets before boarding his Tokyo-bound flight. Keeping bullets in carry-on bags during flight is illegal under U.S. law.

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Police released the man Saturday as he posed no danger of destroying evidence. Police are still investigating how the bullets were undetected when he arrived at Narita.