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

Police at Tokyo's Narita International Airport seized the bullets loaded in two magazines 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 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 later Saturday as he posed no danger of destroying evidence, Ito said. The man and the airline also promised to cooperate in any future investigation. Police are still investigating how the bullets were undetected when he arrived at Narita and went through customs.

American Airlines said in a statement that the crewmember headed to Dallas after his release, but refused to disclose details of his flight out of the U.S. The airline also declined to comment how a crewmember might have walked through U.S. security checks.

U.S. airports are stepping up baggage checks of passengers flying in from overseas.

Police are also considering a possible violation of the Japanese gun and sword control law, but the flight attendant was not charged with any crime.