BANGKOK, Thailand (AP) _ Vietnamese and U.S. experts are conducting their 12th joint search for evidence of what happened to 1,676 Americans missing from the Vietnam War, a U.S. official said today.

Two U.S. military teams arrived in Vietnam on Wednesday for the 15-to-20 day search in six provinces, said the official of the U.S. Embassy in Bangkok, who asked not to be named.

In these searches, investigators inspect plane crash sites, interview villagers who witnessed crashes and collect other evidence of missing soldiers.

The embassy official said Washington hoped that the results of the current search would reflect Vietnamese promises of greater cooperation in joint projects.

Vietnam's Foreign Minister Nguyen Co Thach made the promises in a meeting with U.S. presidential envoy John W. Vessey Jr. in Washington on Oct. 17.

The U.S. military experts are from the Joint Casualty Resolution Center and the Army's Central Identification Laboratory, both based in Hawaii. These agencies are entrusted with accounting for America's wartime missing.

The Army laboratory is still analyzing 10 sets of remains that Vietnam returned Nov. 20, its most recent repatriation, to determine if they are those of missing Americans.

The Pentagon lists 2,294 Americans as missing in action from the war that ended in the Communist defeat of the U.S.-backed South Vietnam government in April 1975. Of the total, 1,676 are missing in Vietnam, 529 in Laos, 83 in Cambodia and six in Chinese coastal waters.

The first joint search was in September 1988, a year after the United States secured a Vietnamese commitment to greater cooperation in return for help with humanitarian problems in Vietnam including rehabilitation of disabled soldiers.