"Spent the day interviewing young N. Koreans who escaped their country. Too many sad stories," journalist Laura Ling of the San Francisco-based online news outlet Current TV wrote on her Twitter page.

But their quest to document the plight of North Korean refugees may have put them in danger. Ling and fellow reporter Euna Lee were still missing Saturday, four days after they reportedly were seized by North Korean soldiers along the border.

A third member of the crew, cameraman Mitch Koss, and a guide eluded capture but were being held in China, the Chosun Ilbo newspaper reported Friday. Their whereabouts were unclear.

Washington is in contact with North Korea about the two detained journalists, State Department officials said.

US 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. There have been a number of contacts made."

The incident comes at a sensitive time on the Korean peninsula, with North Korea declaring its intention to fire a satellite-equipped rocket into space in early April, a launch some fear will be a cover for the test-fire of a long-range missile.

The North also is locked in a standoff with regional powers over its nuclear program, and earlier this week ordered out five U.S. groups that distribute much-needed food aid in a country where the World Food Program says millions are going hungry.

The Rev. Chun Ki-won of the Seoul-based Durihana Mission, a Christian group that helps defectors, said Ling and Lee contacted him three months ago asking for help organizing a trip to China to report on North Korean refugees.

"I exchanged e-mails with the journalists for about three months to coordinate their itineraries, to discuss the news and to give them advice," he said by telephone Friday from the United States.

Chun said he also warned them about the dangers of reporting in the border area.

"I told them to consult with me first if they head toward the border," he said, adding the border region can be "dangerous and difficult for foreigners."

Their first stop: Seoul. "On plane headed to S Korea," Ling, 32, wrote on her Twitter page on March 10.

Chun said they met at his Seoul office the next day, and he helped arrange for them to meet with defectors in South Korea and China.

The Current TV team then hit the road again. "At Seoul airport grubbing on bibimbap & kimchee. Heading to the China/NKorea border. Hoping my kimchee breath will ward off all danger," Ling wrote. The date: Friday the 13th.

Chun said 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.

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. Chun said his group works to help them get asylum.

"Missing home," Ling wrote on Twitter on Monday.

Chun said he spoke to the women by phone early the next morning. They said they were heading to the Chinese border town of Dandong, some 500 miles (800 kilometers) from Yangji, and then on to the city of Shenyang.

That was the last he heard from them.

The North Korean-Chinese border is long, porous and not very well demarcated. The two countries are divided by the Tumen River in North Korea's northeast and by the Yalu to the southwest.

Tens of thousands of North Koreans have streamed across the border into China in recent years, some wading through the Yalu under cover of night, others simply walking across the Tumen, which stays frozen into April.

North Korea border guards have crossed, too, in pursuit of North Koreans — or to rob Chinese towns, coal mines and businesses in the hilly border area.

China often turns a blind eye to foreign journalists trying to report on North Korea from the border, but North Korean guards often react angrily to reporters trying to film or photograph them. Many jeer at journalists and brandish rifles from just steps away.

The Yonhap news agency reported Thursday that the two Americans were detained after ignoring North Korean soldiers' orders to stop filming into North Korea.

In Beijing, an official at the North Korean Embassy refused to comment on the reported detentions.

"If our people took them away, they must have done something that made our people take them into custody," he said. He did not give his name or title, citing embassy policy.

"How do we know whether they crossed into (North Korea) by mistake or were involved in some hostile activities?" he asked.

Ling's father, Doug Ling, said he learned Tuesday that his daughter had been detained. "I worry quite a bit," he told KCRA television in Sacramento.

He said he saw his daughter shortly before she left for what she told him was "a very routine assignment to the North Korean-Chinese border to do a story on the refugees."

Ling's older sister, Lisa Ling, a former co-host of the American TV talk show "The View" and now a correspondent for National Geographic Channel's "Explorer," has declined to comment.

But her Web site, lisaling.com, on Friday featured her account of a 2005 trip to North Korea, a country she described as "the most isolated country on the planet about which very little is known" but the one "I wanted to visit most."

She described how minders were assigned to keep watch on the group, cell phones were confiscated and every conversation was monitored.

A couple of days later, "the feeling of utter isolation hit me," she wrote in a posting removed later Friday.

"Something catastrophic could have happened to my family or in the US and I would have had no way of knowing until I got out. Similarly, something could have happened to me while there ... No one would have known."