CONCORD, N.H - When Tropical Storm Chata'an struck the Federated States of Micronesia in 2002, the U.S. government sent 1,300 blankets, 4,000 disposable diapers, 30 cases of sardines - and my Social Security number.

The nine digits that govern so much of Americans' identities are supposed to be ours for life - and only ours. But mine ended up linked to a Micronesian man who defaulted on a disaster loan from the U.S. Small Business Administration.

I didn't find out until March, in a letter from a debt collector threatening to garnish my wages if I didn't pay $7,306 in two days. The same could happen to an unknown number of others, because of a processing glitch that the U.S. Social Security Administration didn't even know existed and the federal government hasn't fixed.

Who is giving away American Social Security numbers to strangers in other lands? The answer is not so simple.

The problem involves three Pacific island nations, each of which has its own, independent Social Security Administration. The three - the Federated States of Micronesia, the Republic of the Marshall Islands and the Republic of Palau - grant defense rights in the region to the U.S., and in exchange receive aid, including grants and loans after disasters.

For instance, the Federal Emergency Management Agency sent $20 million to 9,700 people in the Federated States of Micronesia after the 2002 storm. The three countries together have received USDA housing grants and loans worth $33 million since 2000.

Some federal agencies collect locally-issued Social Security numbers from grant and loan applicants and report them to credit bureaus as if they were U.S. numbers, regardless of whether the numbers already are in use.

That's the beginning of the problem, which isn't identity theft but can create some of the same headaches when identities become linked in the eyes of lenders or creditors.

"This can really slow you down if there is a default or a history of bad payment," said Chris Jay Hoofnagle, director of information privacy programs at the Berkeley Center for Law and Technology.

The U.S. Department of Agriculture has known for years that it creates "overlapping" Social Security numbers when granting loans in the three island nations, said Donald Etes of the agency's rural development office in Hawaii. The office that processes loans is working on a fix, but there have been no software or policy changes yet, he said.

My own case - involving a Micronesian man who failed to repay an SBA loan - illustrates how the resulting hassles play out and also shows that I'm probably not alone. Of 299 people in Micronesia who took out SBA loans, more than 200 haven't paid up, increasing the odds that others have shared my experience. No one has a good estimate of numbers.

The collection agency told me the debt, though listed under another name, was associated with my Social Security number. Despite knowing I wasn't at fault, I felt my face grow hot as the debt collector rattled off a list of everywhere I had ever lived.

"You've never had any debt like this?" he pressed. "NEVER?"

He backed off within days, but I spent weeks calling and e-mailing federal agencies, banks, credit bureaus and collection agencies in four countries and five time zones trying to untangle the rest. In many cases, no one could explain why it happened, because they weren't convinced it could happen.

It turns out that Social Security numbers in two of the three Pacific Island nations don't even have nine digits like U.S. numbers. They have eight, but some U.S. computers automatically add a zero to the front to fill in the blank.

Sometimes, that creates new numbers beginning with a double-zero - just like New Hampshire's Social Security numbers, and Maine's.

Bottom line: If your U.S. number starts with 002-6, 003-9, 005-7 or 007-8, it could match a number in Micronesia. Numbers that start 006-4 could match numbers in Palau. Those that start with 004 could match numbers in the Marshall Islands.

That works out to roughly 135,000 possible matches, according to an Associated Press comparison of the numbering systems. But no one knows how many actually exist.

Jeff Whitcomb of Keene, N.H., had no idea that public record databases show his Social Security number linked to someone in Micronesia, but he wasn't overly alarmed. As far as he knows, he hasn't been harmed by the connection.

"It seems to me it's likely an innocent mistake, but one that bears watching," he said. "It makes me want to most definitely do business with small, local financial institutions that know me, and not just my Social Security number."

Do other factors contribute to the identity sharing?

The region's major financial player - the Bank of Guam - says it differentiates between local Social Security numbers and U.S. numbers, but won't say how.

None of the three major credit reporting agencies has any way to distinguish between U.S. Social Security numbers and those issued in the three island nations, said industry spokesman Norm Magnuson, who answered questions on behalf of all three agencies.

Surely the four nations' Social Security administrations were aware of this, right? Not a one.

"I thought U.S. government agencies only accepted U.S.-assigned numbers," said Gregory Ngirmang, head of the Republic of Palau Social Security Administration.

The credit bureaus say call the Social Security Administration. But Social Security mainly cares about crediting wages earned by American workers to the right person. If that's not an issue, it's not their problem.

Social Security says try the credit bureaus, or the Federal Trade Commission. But the FTC investigates identity theft, and this isn't theft.

"This is the trouble consumers have. There are obvious questions that need answers, and they don't have to answer you," said Evan Hendricks, author of "Credit Scores and Credit Reports." "You're sort of highlighting how wrong things can go, and how powerless you are to do anything."