The Obama administration set a record for the number of times its federal employees told disappointed citizens, journalists and others that despite searching they couldn't find a single page requested under the Freedom of Information Act, according to a new Associated Press analysis of government data.

In more than one in six cases, or 129,825 times, government searchers said they came up empty-handed last year. Such cases contributed to an alarming measurement: People who asked for records under the law received censored files or nothing in 77 percent of requests, also a record. In the first full year after President Barack Obama's election, that figure was only 65 percent of cases.

The data represents the final figures on the subject that will be released during Obama's presidency. Obama has said his administration is the most transparent ever.

The FBI couldn't find any records in 39 percent of cases, or 5,168 times. The Environmental Protection Agency regional office that oversees New York and New Jersey couldn't find anything 58 percent of the time. U.S. Customs and Border Protection couldn't find anything in 34 percent of cases.

"It's incredibly unfortunate when someone waits months, or perhaps years, to get a response to their request -- only to be told that the agency can't find anything," said Adam Marshall, an attorney with the Washington-based Reporters Committee for Freedom of the Press.

A Justice Department spokeswoman, Beverly Lumpkin, said the administration answered more records requests and reduced its backlog of leftover requests, which should be considered good work on the part of the government in fulfilling information requests.

It was impossible to know whether more requests last year involved non-existent files or whether federal workers were searching less than diligently before giving up to consider a case closed. The administration said it completed a record 769,903 requests, a 19 percent increase over the previous year despite hiring only 283 new full-time workers on the issue, or about 7 percent. The number of times the government said it couldn't find records increased 35 percent over the same period.

"It seems like they're doing the minimal amount of work they need to do," said Jason Leopold, an investigative reporter at Vice News and a leading expert on the records law. "I just don't believe them. I really question the integrity of their search."

In some high-profile instances, usually after news organizations filed expensive federal lawsuits, the Obama administration found tens of thousands of pages after it previously said it couldn't find any. The website Gawker sued the State Department last year after it said it couldn't find any emails that Philippe Reines, an aide to Hillary Clinton and former deputy assistant secretary of state, had sent to journalists. After the lawsuit, the agency said it found 90,000 documents about correspondence between Reines and reporters. In one email, Reines wrote to a reporter, "I want to avoid FOIA," although Reines' lawyer later said he was joking.

When the government says it can't find records, it rarely provides detailed descriptions about how it searched for them. Under the law, federal employees are required to make a reasonable search, and a 1991 U.S. circuit court ruling found that a worker's explanation about how he conducted a search is "accorded a presumption of good faith, which cannot be rebutted by purely speculative claims" that a better search might have turned up files.

Skepticism has led many experts increasingly to specify exactly how they want federal employees to search for files: Which offices and filing cabinets, which hard drives, whose email inboxes, even what keywords to type in search software. To do otherwise means relying on overworked government staff to figure out how best to proceed.

"They do really crappy searches," said Washington lawyer Kel McClanahan of National Security Counselors Inc., which handles transparency and national security cases. He lost a federal appeals case in November on behalf of a U.S. citizen, Sharif Mobley, trying to obtain U.S. records that might show why he has been imprisoned in Yemen since 2010. The court said the FBI wasn't required to search for files in locations and ways Mobley's lawyers wanted.

Under the records law, citizens and foreigners can compel the U.S. government to turn over copies of federal records for zero or little cost. Anyone who seeks information through the law is generally supposed to get it unless disclosure would hurt national security, violate personal privacy or expose business secrets or confidential decision-making in certain areas.

The AP's annual review covered all requests to 100 federal agencies during fiscal 2015. The administration released its figures ahead of Sunshine Week, which ends Sunday, when news organizations promote open government and freedom of information.

Overall, the Obama administration censored materials it turned over or fully denied access to them in a record 596,095 cases, or 77 percent of all requests. That includes 250,024 times when the government said it couldn't find records, a person refused to pay for copies or the government determined the request to be unreasonable or improper. The White House routinely excludes those cases from its own assessment. Under that calculation, the administration said it released all or parts of records in 93 percent of requests.

More than half of federal agencies took longer to answer requests last year than the previous year.