An unknown tech-savvy person -- possibly someone with high-level access to New Orleans' City Hall computer system -- deliberately removed New Orleans Mayor Ray Nagin's e-mail and other material, two experts hired to recover the information said Wednesday.

"It had to be a human action. This was not data that disappeared because of damage to the store or by accident," said Christopher Reade, a partner in Carrollton Technology Partners, who has participated in the project to recover the information.

"This had to be something that someone would actually do," he said at a news conference. "You can't just hit 'delete' in your computer and it goes away. It requires you to run programs against these databases (in the City Hall system) to remove it. That's why I say it's not an action that would be taken by accident."

The data were removed sometime between June 2008, when the previous e-mail system was damaged, and May 11, when the Louisiana Technology Council started work to recover the information, council president Mark Lewis said at a news conference.

The box containing Mayor Ray Nagin's e-mail was the only one of 59 mailboxes that was missing, Reade said.

Whoever did it would have needed "administrative-level access" to the e-mail servers, Reade said. Neither he nor Lewis would speculate on who might have done it.

"The average person, even the average techie, would not know how to do that," Reade said.

WWL-TV sued Nagin after his administration failed to respond to a public-records request for his e-mail messages and appointments calendar from last year.

During the news conference, Lewis and Reade praised the personnel in the city's information technology department, with whom they have worked to try to recover the information.

"We have no reason to believe that any of the folks working with us at City Hall are involved in any deletion of data," Lewis said.

The team was able to recover the mayor's calendar and other material, but not his e-mail, both men said.

Although the quest for the missing messages continues, Lewis declined to speculate on the chances of finding them.

The Nagin administration in mid-April hired LTC to conduct a "forensic review" of the city's computer-network servers to try to retrieve messages "sent or received by the mayor." Working in city technology offices for the past six weeks, LTC analysts pored over hundreds of gigabytes of data in search of the missing messages and calendar entries.

The men said they expect to finish their work and submit a report to City Hall within a week or so.

The FBI is also investigating the case, but neither Lewis or Reade would speculate on the agency's investigation.

FBI spokeswoman Sheila Thorne declined to comment.

Ceeon Quiett, Mayor Nagin's spokeswoman, could not be reached for comment.