Three workers who died Saturday after collapsing inside an ore carrier vessel docked at a smelter in Oita…suffocated due to lack of oxygen…The Oita prefectural police made the announcement after inspectors…began an on-site examination of the ship at the facility of Nikko Seiren [part of Pan Pacific Copper]...The three, all employees of a Nikko Seiren subsidiary, lost consciousness and collapsed…as they entered the ship's hold that contained about 5,900 tons of copper concentrate…