NAHA, Okinawa (Kyodo) A university student from Yokohama picked up a decayed grenadelike object on the shore of Okinawa Island during a sightseeing tour and took it with him on a flight to a remote island, police said Monday.

"I picked it up because I thought it was seashell. I then found that it might be a grenade, but thought I shouldn't leave it there. I didn't think it might explode," he told reporters.

The student, 20, picked up the object, which was corroded and covered with seaweed, on the shore in Yomitan on Okinawa Island on March 16. He checked his baggage containing the object on a Japan Transocean Air flight from Naha to remote Ishigaki Island on Saturday.