A bomb threat aboard a cruise ship bound for Israel prompted the authorities to launch a security operation in the port of the Greek island of Syros yesterday, after an unknown person claimed that an explosive device had been attached to the ship's hull, the Greek authorities said. Initial tests did not result in the discovery of explosives. It is expected that further tests will be conducted before the ship can resume its journey. The ship, flying the Panamanian flag, was supposed to sail to Haifa with 940 passengers and 597 crew members on board when the threat was received.