The Census Bureau turned over confidential information including names and addresses to help the Justice Department, Secret Service and other agencies identify Japanese-Americans during World War II, according to government documents released today.

Documents found by two historians in Commerce Department archives and the Franklin D. Roosevelt Presidential Library confirm for the first time that the bureau shared details about individual Japanese-Americans after Japan's attack on Pearl Harbor on Dec. 7, 1941.

The Census Bureau played a role in the confinement of more than 100,000 Americans of Japanese descent who were rounded up and held in internment camps, many until the war ended in 1945. In 1942, the census turned over general statistics about where Japanese-Americans lived to the War Department. It was acting legally under the Second War Powers Act, which allowed the sharing of information for national security.

The newly released documents show that in 1943, the census complied with a request by the Treasury Department to turn over names of individuals of Japanese ancestry in the Washington, D.C., area because of an unspecified threat against President Franklin Roosevelt. The list contained names, addresses and data on the age, sex, citizenship status and occupation of Japanese-Americans in the area.

"The issue is how ethical is it to use the census to target people," said William Seltzer, a statistician at Fordham University who co-authored the report with Margo Anderson, professor of history and urban studies at the University of Wisconsin-Milwaukee.

Sharing the information was not illegal, Seltzer said, but "it was ethically questionable."

The Census Bureau's role in helping the government ferret out Japanese-Americans during the war has been documented in previous research by Seltzer and Anderson and others. But today's report marks the first time that documents have been uncovered indicating that the agency released actual names.

The Census Bureau has consistently denied releasing such names probably because, over time, most officials there probably didn't know it had happened, Seltzer said.

The agency has "not had the opportunity to review" today's report, said Christa Jones, chief of the census policy office.

Census activities during World War II "obviously go against their own mandate for confidentiality," said Terry Ao, director of census and voting programs at the Asian American Justice Center, a civil-rights group.

"Actions such as this have the potential of having a very serious detrimental impact on the ability of the Census Bureau to collect data that we need. The most important thing about this would be that the (agency) today understands it has no authority to conduct such activity. They do take their legal obligations for confidentiality very seriously. "

The census every 10 years asks Americans to fill out detailed questionnaires that probe everything from their income and household relationships to occupation, race and ethnicity. The information is used to allocate federal funds and congressional seats, draw political districts, track changes in family size and plan for roads and schools.

The report by Seltzer and Anderson comes as a revelation to Kenneth Prewitt, a public-affairs professor at Columbia University who was census director during the 2000 census.

Seven years ago, Prewitt dealt with controversy over census questionnaires. Then-Senate Majority Leader Trent Lott, R-Miss., urged people to skip any census questions they felt violated their privacy. The objections were exacerbated by previous research by Seltzer and Anderson on the census' role in the internment of Japanese-Americans.

Prewitt apologized for what the bureau had done, something no census official had done previously. He called the new report "a remarkable piece of historical detective work" but is saddened by the findings because the census prides itself on keeping all information confidential.

"It is better to know than to not know," he said. "Knowing the facts will redouble the effort to assure it is not repeated."

After the Sept. 11 attacks, Congress approved the Patriot Act to give the government broad investigative powers. Since then, civil-liberties groups have criticized government efforts to monitor phone calls, prepare no-fly lists and keep files on anti-war activists.

"It's a bombshell," Caroline Fredrickson, director of the ACLU's Washington Legislative Office, said of today's disclosures. "This is such a black mark on American history that we need to make sure we never allow ourselves to engage in anything close to that kind of violation of people's constitutional rights."

An ethical issue was raised in 2004 when the census turned over information it had collected about Arab-Americans by ZIP code but not by name. The information was already public but civil-rights groups protested the agency's handing over of data to Homeland Security.

The census now puts all requests for sensitive data through a rigorous approval process and makes all special releases of data available to the public.