These undated photo show two American journalists Laura Ling, rigtht, and Euna Lee. Ling and Lee were detained by North Korean soldiers while on a reporting trip earlier in the week near the country's border with China, South Korean news reports said Thursday, March 19, 2009.(AP Photo/Yonhap)

SEOUL, South Korea — Two American journalists were missing Friday after they reportedly were detained by North Korea for ignoring warnings to stop shooting footage of the reclusive country.

Journalists Laura Ling and Euna Lee, reporters for former Vice President Al Gore's online media outlet Current TV, were seized Tuesday along the Chinese-North Korean border, according to news reports and an activist who had worked with them. Their Chinese guide also was detained although a third journalist with the group, Mitch Koss, apparently eluded capture.

U.S. officials expressed concern to North Korean officials about the reported detentions and said they were working with the Chinese government to ascertain the whereabouts of the Americans.

"When you have two American citizens who are being held against their will, we want to find out all the facts and gain their release," State Department spokesman Robert A. Wood said Thursday in Washington.

U.S. officials also were in contact with Swedish diplomats in North Korea. Sweden's Ambassador to Pyongyang, Mats Foyer, refused to say in an e-mail whether negotiations for the Americans' release were under way but acknowledged that Sweden acts as Washington's representative because the U.S. does not have diplomatic relations with North Korea.

Calls to North Korea's mission to the United Nations in New York went unanswered Thursday.

In San Francisco, an employee of Current TV told reporters: "There will be no comment on the situation anytime today."

Ling is a sister of Lisa Ling, a former co-host of the American TV talk show "The View" and now a contributing correspondent for National Geographic Channel's "Explorer" TV show. She said the family had no comment.