An inter-Korean factory zone in North Korea began its trial-run production on Monday after a five-month hiatus, as the two Koreas discuss ways to ensure sustainable growth of the joint economic venture, Yonhap News Agency reported. More than half of the 123 South Korean firms with factories at the Kaesong Industrial Complex in the North\'s border city were set to start trial operations, with the aim of fully normalizing operations thereafter, the South Korean Unification Ministry said. 821 South Korean managers and workers had plans to cross over the border into Kaesong during the day, with more than 400 to stay overnight to oversee production normalize there, the ministry and customs office said. The resumption came after Seoul and Pyongyang agreed last Tuesday to begin operations after talks made headway on setting up safeguards to ensure that the complex will not be shut down again due to non-economic reasons. All operations at Kaesong, which first began production in late 2004, came to a screeching halt on April 9, when the North pulled out all of its 53,000 workers from the park at the height of political and military tension on the Korean Peninsula. On the reopening of the complex, businessmen said they were relieved that cross-border talks in the past few months have reached a breakthrough in resolving differences. In addition to the reopening of the industrial park, the two sides began the third round of joint management committee negotiations with the aim of enhancing the rights of South Korean workers at Kaesong. The committee gives Seoul equal say in the running of the complex that in the past was effectively run by Pyongyang. The two Koreas still remain technically at war after the 1950-53 Korean War ended in a truce.