Updated

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 U.S. 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 U.S.-South Korean military exercises.

The two female U.S. 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.

A U.S. Embassy spokesman in Seoul said he had no further information. He asked not to be named, citing the sensitivity of the issue.

South Korean media and a South Korean missionary identified the two Americans as Laura Ling and Euna Lee, reporters for former Vice President Al Gore's San Francisco-based media outlet Current TV.

State Department officials said Washington is in contact with North Korea about the detentions.

U.S. Secretary of State Hillary Rodham Clinton "is engaged on this matter right now," spokesman Robert A. Wood told reporters Friday. "There is a lot of diplomacy going on." He did not elaborate.

The two reporters were in the border area with a male cameraman and their guide as part of a reporting assignment on North Korean refugees.

The journalists headed to the Chinese city of Yanji, across the border from North Korea's far northeastern corner, where they planned to interview women forced by human traffickers to strip for online customers, according to the Rev. Chun Ki-won of the Seoul-based Durihana Mission, a Christian group that helps defectors.

Chun said Ling and Lee contacted him three months ago asking for help organizing a trip to China.

They also planned to meet with children of defectors, Chun said. Many children who grow up on the run in China live in legal limbo, unable even to attend school, according to a 2008 Human Rights Watch report.

The journalists and cameraman Mitch Koss were following a guide across the frozen Tumen River early Tuesday morning when North Korean soldiers armed with rifles approached them from a half-hidden guard post, the Chosun Ilbo newspaper reported Saturday. It cited activists working with North Korean refugees in China and other unidentified sources.

Koss and the guide pushed the North Korean soldiers away and ran back toward China, but Ling and Lee were caught, the newspaper said, citing an unidentified source.

Koss and the guide were later seized by Chinese border guards and sent to the Chinese Public Security Bureau, the newspaper said. Their whereabouts remain unclear.

The North Korean-Chinese border is long, porous and not well demarcated and thus a common route for escape from the North.

A growing number of North Koreans have sneaked into China to avoid political repression, chronic food shortages and to seek asylum, mostly in South Korea, according to North Korean defectors in South Korea and activists.