North Korea detained two Americans for illegally crossing its border and is investigating them, the communist country's official news agency said Saturday. The arrests come at a sensitive time, with the North planning on firing a satellite-equipped rocket into space in early April - a launch some fear will be a cover for testing missile technology. The North also is locked in a standoff with regional powers over its nuclear program, and earlier this week expelled five US groups that distribute much-needed food aid in a country where the World Food Program says millions are going hungry. It has also repeatedly shut its southern border in recent days to protest joint US-South Korean military exercises. The two female US journalists were arrested March 17 while "while illegally intruding into the territory" of North Korea after crossing the border with China, the Korean Central News Agency said. Authorities were investigating, KCNA said. The brief dispatch gave no further details.