Julia Campbell, 40, of Fairfax, Va., was last seen on April 8 in the town of Banaue in Ifugao province, where she had planned to hike alone, said U.S. Embassy spokesman Matthew Lussenhop.
The area, about 160 miles north of Manila, is famed for its mountainside rice terraces and pine forests. The armed wing of the Communist Party - the New People's Army - also operates there.
In 1990, the New People's Army seized Peace Corps volunteer Timothy Swanson and held him for 50 days on central Negros island. He was released unharmed to the Red Cross.
Lussenhop said the Peace Corps started looking for Campbell after she missed appointments on April 11.
"Embassy security officials and Peace Corps security and local authorities are in that region right now looking for her or finding people who may know where she is," he said. Regional police commander Chief Superintendent Raul Gonzales said at least four teams from the provincial police office have been mobilized for the search, after the U.S. Embassy told them Campbell was missing. He said the directive to conduct the search came from the national police headquarters in Manila. Maj. Gen. Rodrigo Maclang said members of an army company in Banaue also joined the search Saturday, after receiving an order from the military's Northern Luzon Command. A military helicopter will help with the search, he said. "We were unaware of the incident. We learned only today that someone has been missing," he said. Maclang said there is only a small military presence in area because "it is not a major concern now with regard to the insurgency." As early as Thursday, local police started checking the guest registries in hotels and inns for Campbell's name, receptionist Lea Ananayo at the Halfway Lodge in Banaue said by telephone. Authorities also left Campbell's photos to be displayed in hotel lobbies, shops and market stalls in the town. Campbell has been teaching college in Albay province's Legazpi city, southeast of Manila, since March 2005. She was planning to hike in a hilly area near Batad village, about a mile east of Banaue's town center, the embassy said. The embassy appealed to the public for any information on the welfare and whereabouts of Campbell. It offered a reward, but did not specify an amount. Campbell, who worked as a journalist in New York, contributed a story to CNN about the death and destruction in the wake of supertyphoon Durian, which hit Legazpi in late November. Writing in her Internet blog, she said she "decided to step out of the rat race of New York" to join the Peace Corps when she was 38. In an entry on May 27, 2005, two months after her arrival in the Philippines, she expressed anticipation about no longer having "the comfort of fellow Americans within reach." "I will be left to my own devices in a strange place with people and a culture I barely know," she wrote. Campbell is one of 137 Peace Corps volunteers currently in the Philippines. More than 8,000 Peace Corps volunteers have served in the Philippines since 1961, making it the corps' second-oldest program in the world, the embassy said. AP-ES-04-14-07 2004EDT