SAN DIEGO -- The U.S. Attorney's Office is looking into allegations that San Diego city employees illegally destroyed documents that were part of a federal investigation. Insiders told 10News that this has happened more than one time.

According to sources, it was a way of doing business. An unwritten policy. If there was something you did not want the public to see, get rid of it.

Employees at San Diego City Hall write thousands of e-mails and produce nearly as many printed documents every day.

Last year, federal subpoenas ordered two dozen city employees to turn over certain records dating back to 1996.

New City Attorney Mike Aguirre pledged to help federal investigators and found 25 boxes of records he says were supposed to be turned over months earlier.

Last week he dropped another bombshell on City Hall -- allegations of wholesale document destruction at financial manager Mary Vattimo's office -- in violation of the subpoenas.

Now a new subpoena from the U.S. Attorney is telling the city clerk to submit all documents previously ordered and to bring them to the federal grand jury's offices on Thursday.

"I've been told the paperwork is paperwork that has already been submitted," City Manager Lamont Ewell said.

Ewell oversees two of the offices where records were found and where others were allegedly destroyed. He said his staff told him it has all been done by the book.

"There was set of protocol that was established with the SEC and the U.S. Attorney's Office that did not change and they have assured me that they followed that protocol," Ewell said.

But it may go much deeper, according to 10News.

One city worker 10News spoke with said shortly after the first subpoenas came out in April of 2004, paper shredders were literally breaking down at offices in City Hall and at the City Attorney's Office because people were shoving too many documents in them. He said maintenance crews were working overtime fixing the shredders.

Employees in both the former City Attorney's Office and City Hall confirm records were being destroyed, 10News reported. Ewell maintains nothing has been proven.

"If there are facts that suggest that anyone did anything wrong we will deal with that," Ewell said.

The most recent subpoena is also very specific about wanting to know how city employees were instructed to handle records that might be part of the investigation and especially about files that may have been destroyed last month.