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.

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.