Navy spokesman Ayo Olugbode said several agencies are working on a joint search operation to locate the crew kidnapped Saturday. They were aboard the Swiss-owned MV Glarus carrying wheat while sailing from Lagos to Port Harcourt in southern Nigeria. The crew members are nationals of Philippines, Slovenia, Ukraine, Romania, Croatia, and Bosnia, the Nigerian Maritime Administration and Safety Agency said in a statement released to Reuters news agency. The pirates reportedly struck about 45 nautical miles south-southwest of Bonny Island.Preliminary investigations into Saturday's incident show the crew members had been taken to land, Olugbode said. "We are working with many agencies including with Interpol on search and rescue operations on this case," Olugbode said.The spokesman said he had no information on any ransom demands. "We are speaking with the remaining crew members to know what measures were taken during the attack. For instance, the captain and the ship's crew are to go into the citadel of the ship when they are being attacked. We want to know if all these steps were taken during the incident," Olugbode told CNN.Although maritime piracy and armed robbery incidents dropped to a 22-year-low last year, danger still persists to vessels plying routes in the Gulf of Guinea, especially off Nigeria, the International Maritime Bureau (IMO) said in a recent report.According to the non-profit devoted to fighting crime at sea, 10 incidents of kidnapping involving 65 crew members were reported in or around Nigerian waters in 2017.In February, 22 Indian nationals were taken hostage on an oil vessel off the coast of West Africa.They were released around a week later by the pirates who also hijacked the vessel.