An unidentified number of US intelligence agents are now in South Korea, collecting North Korea-related information, Yonhap News reported Wednesday, citing unnamed sources at the Seoul government.Their mission also includes a review, and possibly an update, of emergency evacuation plans for over 200,000 Americans residing here, it said.Some of the agents – belonging to either the Central Intelligence Agency or the Department of Homeland Security -- were dispatched early last month after the North threatened to create with its missiles an “enveloping fire” near the US territory of Guam. Some others arrived after Pyongyang conducted an underground nuclear weapons test Sunday, dramatically upping the ante in its military standoff with the US.Earlier this year, the CIA created the Korea Mission Center to beef up its intelligence on the peninsular affairs.