The U.S. State Department says it is in contact with North Korea about two U.S. journalists taken into custody by Pyongyang.
A State Department official says the United States has contacted North Korea through its mission to the United Nations in New York. The official says Secretary of State Hillary Clinton is very involved in the case, noting she is having phone conversations with relevant parties.
Media reports say U.S. journalists Laura Ling and Euna Lee were detained Tuesday with their Chinese guide near the Tumen River, along North Korea's border with China. It is unclear whether they were on the Chinese or North Korean side of the river.
The journalists were reportedly working on a story on North Korean refugees, many of whom try to escape the country by crossing the river into China.
The two were said to have ignored warnings from North Korean guards to stop filming. Reports say a fourth person escaped arrest.
China has said it is also investigating the matter.
The United States and North Korea have no official diplomatic ties but communicate through their delegations at the United Nations in New York, and through the Swedish embassy in Pyongyang, which represents U.S. interests in North Korea.
Ling and Lee were working for an online news company - Current TV - that is based in the western U.S. state of California. Current TV was co-founded by former U.S. Vice President Al Gore.
The incident comes at a sensitive time for U.S.-North Korean relations, with the communist state preparing what it calls a satellite launch early next month. The U.S. and South Korea say the launch is a cover for a test of the North's longest-range missile.