Venezuela Intercepts Ship With 5 Americans Aboard CARACAS, Venezuela - Maps of Venezuela hanging on the walls of schoolrooms and in government offices show a large striped area to the east of the country's border with Guyana marked "Zone in Reclamation." For more than a century, Venezuela has claimed that it is the rightful owner of this zone, which consists of about three-quarters of Guyana's national territory. The longstanding feud has often darkened relations between the two nations. Now, five Americans on a research ship working under an oil exploration contract with the Guyanese government appear to have become ensnared in this dispute, which also involves clashing claims over territorial waters off Guyana's coast and the right to drill for oil there. The Guyanese Foreign Ministry said in a statement Friday that a Venezuelan naval vessel, the Yekuana, had obstructed the research ship's passage in Guyanese waters a day earlier. The Venezuelan ship then began escorting the research ship toward Margarita Island in Venezuela, according to the statement, which said the crew was under arrest. The research ship, the MV Teknik Perdana, had about 39 people on board, including five Americans, according to Peter Tatro, operations director of TDI-Brooks International, a Texas company that had chartered the vessel. Mr. Tatro said that the Panamanian-flagged ship had been surveying the seafloor in preparation for possible oil exploration, and that TDI-Brooks was working for the Anadarko Petroleum Corporation, which has a contract with Guyana to search for oil in the area. Everyone on board the ship was safe, Mr. Tatro said. The Guyanese Foreign Ministry said that the research ship "was in Guyana's waters when this incident took place." Calling the Venezuelan action "a serious threat to the peace of this subregion," the statement called for the return of the ship and its crew. But the Venezuelan Foreign Ministry later released a statement saying the research ship had been operating in a zone controlled by Venezuela, and it protested "the activities of scientific prospecting and exploration of the Venezuelan continental shelf and seafloor." It said the ship was expected to arrive at Margarita Island on Saturday morning. Mr. Tatro said that the encounter between the two ships did not involve violence. "There were instructions provided and it was pretty explicit, but there were no shots fired of any kind," he said. There were no threats. Nobody's been harmed or pushed around. It's been pretty low key in that regard. The State Department and the American Embassy in Caracas did not respond to requests for comment. The dispute dates at least to the 18th century, when Spain and Holland skirmished over colonial boundaries in South America, and continued after gaining independence from Britain. More recently it has served as a periodic shibboleth for Venezuelan patriots eager to wave the flag. President Hugo Chávez, who died in March, occasionally appeared on television sitting in front of a large Venezuelan map, with the candy-cane-striped reclamation zone clearly visible over his shoulder, like a territorial appendix. Friction increased recently after Guyana signed contracts to begin offshore oil exploration. In August, Mr. Chávez's successor as president, Nicolás Maduro, traveled to Georgetown, Guyana, where he met with President Donald R. Ramotar of Guyana. Mr. Maduro later said the differences between the countries would be resolved through diplomacy. He was criticized here by the political opposition for not pressing the territorial issue and demanding a halt to oil exploration. Guyana has a population of 800,000 and is roughly the size of Kansas; the reclamation zone claimed by Venezuela, which includes the territory west of the Essequibo River, is about the size of Georgia. Venezuela, a major oil producer, is much larger, with an area about the size of Arizona, Nevada and New Mexico combined and a population of about 29 million. María Eugenia Díaz contributed reporting.