Taiwan's military must investigate further to find out what General Lo leaked in what officials call their worst spy case ever, says deputy defense minister Andrew Yang.
Lo had met Chinese counterparts offshore, complicating the case, says Mr. Yang. He adds that the probe may point to additional suspects but would not specify what information might have been leaked.
Taiwan media says Lo, undetected because of his rank, turned over material on a Taiwan-US Pacific Command joint military strike information-sharing platform, proposed sales of Apache helicopters made by Boeing and an island-wide optical cable network.
China has claimed Taiwan since Chiang Kai-shek's Nationalists fled to the island after losing the Chinese civil war to Mao Zedong's Communists. Both sides continue to arm themselves in case of war with the other side just 160 km (100 miles) away.
Even as relations have warmed quickly since 2008 through trade talks under Taiwan's China-friendly President Ma Ying-jeou, the two historic foes have avoided discussion of far more sensitive military issues.