Some of President Barack Obama’s political appointees are using secret government email accounts to conduct official business, a practice that complicates agencies’ legal responsibilities to find and turn over emails under public records requests and congressional inquiries.

White House spokesman Jay Carney on Tuesday acknowledged the practice and said it made eminent sense for Cabinet secretaries and other high-profile officials to have what he called alternative email accounts that wouldn’t fill with unwanted messages. Carney said all their email accounts, public and otherwise, were subject to congressional oversight and requests by citizens under the U.S. Freedom of Information Act.

“There’s nothing secret,” Carney said.

The Associated Press reviewed hundreds of pages of government emails released under the federal open records law and couldn’t independently find instances when material from any of the secret accounts it identified was turned over. Congressional oversight committees said they were unfamiliar with the few nonpublic government addresses that AP identified so far, including one for Secretary Kathleen Sebelius of the Health and Human Services Department.

The White House said the practice also was used by previous administrations, but its scale across the government remains a mystery: Most federal agencies have failed to turn over lists of political appointees’ email addresses, sought under the Freedom of Information Act more than three months ago. The Labor Department initially asked the AP to pay more than $1 million for its email addresses.

The AP asked for such addresses after last year’s disclosures that former chiefs at the Environmental Protection Agency had used separate email accounts at work. The practice is separate from officials who use personal, nongovernment email accounts for work, which generally is discouraged because of laws requiring that most federal records be preserved.

Having separate accounts could put an agency in a difficult spot when it is compelled to search for and release emails as part of congressional or internal investigations, civil lawsuits and public records requests. That’s because employees assigned to compile such responses would need to know about the accounts to search them.

“What happens when that person doesn’t work there anymore? He leaves and someone makes a request (to review emails) in two years,” said Kel McClanahan, executive director of National Security Counselors, an open government group. “Who’s going to know to search the other accounts? You would hope that agencies doing this would keep a list of aliases in a desk drawer, but you know that isn’t happening.”

Agencies where secret addresses have been identified, including the Labor Department and HHS, said maintaining nonpublic email accounts allows senior officials to keep separate their internal messages with agency employees from emails they exchange with the public. They also said public and nonpublic accounts would always be searched in response to official requests and the records would be provided as necessary.

In its review, the AP found only one instance of a secret address being published: An email from Labor Department spokesman Carl Fillichio to 34 co-workers in 2010 was turned over to an advocacy group, Americans for Limited Government. It included as one recipient the nonpublic address for Seth D. Harris, now the acting labor secretary, who maintains at least three separate email accounts.

Ten agencies have not yet turned over lists of email addresses, including the Environmental Protection Agency and the departments of Defense, Veterans Affairs, Transportation, Treasury, Justice, Housing and Urban Development, Homeland Security, Commerce and Agriculture. All have said they are working on a response.

Carney would not say whether White House officials also use secret accounts, noting that the president’s staff, like Congress, is exempt from turning over materials under the open records law. But Carney said that early in his tenure as press secretary, after his email address had been announced publicly, Carney changed his address to avoid being inundated by emails and spam.

“That’s a very reasonable thing to do,” Carney said.

Courts have consistently set a high bar for the government to withhold public officials’ records under the federal privacy rules. A federal judge, Marilyn Hall Patel of California, said in August 2010 that “persons who have placed themselves in the public light” — such as through politics or voluntarily participation in the public arena — have a “significantly diminished privacy interest than others.” Her ruling was part of a case in which a journalist sought FBI records but was denied them.