WASHINGTON – As the nation marks the 30th anniversary of the end of U.S. involvement in the Vietnam War, the government continues to search for the 1,835 prisoners of war and missing military personnel who – dead or alive – remain somewhere in Southeast Asia.

The nerve center of the search is the Pentagon’s Defense Prisoner of War-Missing Personnel Office, based in Arlington, Va., which uses its 600-member staff spread throughout the world to sift through pages of documents, years of memories, grains of soil and strands of DNA in an attempt to uncover clues that would bring the missing persons home.

While all of the cases of missing servicemen are active, the more details known about the case, including when, where and how the person went missing and if the missing was last seen alive or dead, the greater likelihood the U.S. government will be able to convince a former enemy that it should dig up the country looking for lost soldiers, sailors, Marines and airmen, said Larry Greer, spokesman for the Missing Personnel Office.

“We would not allow the Vietnamese to come into the United States and start digging up what they thought were gravesites in the middle of the Pentagon,” Greer said in an interview. “Likewise they don’t allow us to, but what they do is they try to provide us information gathered by their sources so we can be satisfied, if we trust the information, that we know enough about the case in there, and then we can decide to pursue it.”

Excavations can start only after an investigation has been narrowed to a specific area and enough evidence exists to suggest “there is a good chance we’re going to find the remains,” Greer said. “We can’t send a very expensive team of 100 people, 100 specialists, into an area and say, ‘OK, everybody go out and just start poking.'”

Of the 18 Maine residents missing at the end of the Vietnam War 30 years ago today, four have been accounted for.

The search goes on for not only Vietnam servicemen, but also the 128 Cold War missing, the 8,152 Korean War missing, and the more than 78,000 missing from World War II.

For some groups, the office’s carefully considered approach, mixing economic prudence with sensitive diplomacy and a slow investigative process, is not good enough. They say the government should be spending and doing more to bring those lost service people home.

Recently, the National League of POW/MIA Families expressed in its newsletter a lack of confidence in Deputy Assistant Secretary of Defense Jerry Jennings, who heads the POW/MIA office, complaining that he seemed unable to work with families of the missing and seemed to be easing pressure on host nations, such as Vietnam, to turn over information that could lead to the whereabouts of missing servicemen.

Since the end of the Vietnam War, 748 of the 2,583 initially missing have been accounted for, according to the office’s Web site.

Jennings could not be reached for comment because he is on indefinite medical leave, but Greer, the department’s spokesman, responded for the department.

“I’ve been here 10 years and worked for three senior leaders,” including Jennings, Greer said. Jennings “has traveled more, and met with more senior officials of more foreign governments, than any of our previous leaders. He has led initiatives into areas where doors were previously closed to us and to our recovery operations.”

In the 10 years the United States has been working in North Korea, the office has recovered the remains of more than 200 soldiers. Additionally, the office has gained access to documents in Russian, Vietnamese and Laotian archives, which had not been available before, Greer said.

Efforts to bring a full accounting of the missing costs the government $105 million a year, Greer said. This covers not only the cost of excavations but also the expense of identifying remains sent to labs in Hawaii and Virginia through DNA and other means and of tracing artifacts, such as buttons, fabric, and boots, back to the war, branch, and unit of the deceased serviceman.