CBS) This is the story of hundreds, if not thousands, of foreign language documents that the FBI neglected to translate before and after the Sept. 11 attacks -- documents that detailed what the FBI heard on wiretaps and learned during interrogations of suspected terrorists.

Sibel Edmonds, a translator who worked at the FBI's language division, says the documents weren't translated because the division was riddled with incompetence and corruption.

Edmonds was fired after reporting her concerns to FBI officials. She told her story behind closed doors to investigators in Congress and to the Justice Department. Most recently, she spoke with the commission investigating the Sept. 11 attacks.

She first told Correspondent Ed Bradley her story a year after Sept. 11.

Because she is fluent in Turkish and other Middle Eastern languages, Edmonds, a Turkish-American, was hired by the FBI soon after Sept. 11 and given top-secret security clearance to translate some of the reams of documents seized by FBI agents who have been rounding up suspected terrorists across the United States and abroad.

Edmonds says that to her amazement, from the day she started the job, she was told repeatedly by one of her supervisors that there was no urgency -- that she should take longer to translate documents so that the department would appear overworked and understaffed. That way, it would receive a larger budget for the next year.

“We were told by our supervisors that this was the great opportunity for asking for increased budget and asking for more translators,” says Edmonds. “And in order to do that, don't do the work and let the documents pile up so we can show it and say that we need more translators and expand the department.”

Edmonds says that the supervisor, in an effort to slow her down, went so far as to erase completed translations from her FBI computer after she'd left work for the day.

“The next day, I would come to work, turn on my computer, and the work would be gone. The translation would be gone,” she says. “Then I had to start all over again and retranslate the same document. And I went to my supervisor and he said, ‘Consider it a lesson and don't talk about it to anybody else and don't mention it.’

"The lesson was don’t work, and don’t do the translations. ...Don't do the work because -- and this is our chance to increase the number of people here in this department."

Edmonds put her concerns about the FBI's language department in writing to her immediate superiors and to a top official at the FBI. For months, she said she received no response. Then, she turned for help to the Justice Department's inspector general and to Sen. Charles Grassley, whose committee, the Judiciary Committee, has direct oversight of the FBI.

“She's credible,” says Grassley. “And the reason I feel she's very credible is because people within the FBI have corroborated a lot of her story.”

The FBI has conceded that some people in the language department are unable to adequately speak English or the language they're supposed to be translating. Kevin Taskasen was assigned to Guantanamo Bay in Cuba to translate interrogations of Turkish-speaking al Qaeda members who had been captured after Sept. 11. The FBI admits that he was not fully qualified to do the job.

“He neither passed the English nor the Turkish side of the language proficiency test,” says Edmonds.

Critical shortages of experienced Middle Eastern language translators have plagued the FBI and the rest of the U.S. intelligence community for years.

Months before the first World Trade Center bombing in 1993, one of the plotters of the attack was heard on tape having a discussion in Arabic that no one at the time knew was about how to make explosives -- and he had a manual that no one at the time knew was about how to blow up buildings. None of it was translated until well after the bombing, and while the FBI has hired more translators since then, officials concede that problems in the language division have hampered the country's efforts to battle terrorism.

According to congressional investigators, this may have played a role in the inability to prevent the Sept. 11 attacks. The General Accounting Office reported that the FBI had expressed concern over the thousands of hours of audiotapes and pages of written material that have not been reviewed or translated because of a lack of qualified linguists.

“If they got word today that within, in a little while, the Hoover Dam was going to be blown up, and it takes a week or two to get it translated, as was one of the problems in this department, you know, you couldn't intervene to prevent that from happening,” says Grassley.

In its rush to hire more foreign language translators after Sept. 11, the FBI admits it has had difficulty performing background checks to detect translators who may have loyalties to other governments, which could pose a threat to U.S. national security.

Take the case of Jan Dickerson, a Turkish translator who worked with Edmonds. The FBI has admitted that when Dickerson was hired, the bureau didn't know that she had worked for a Turkish organization being investigated by the FBI's own counter-intelligence unit.

They also didn't know she'd had a relationship with a Turkish intelligence officer stationed in Washington who was the target of that investigation. According to Edmonds, Dickerson tried to recruit her into that organization, and insisted that Dickerson be the only one to translate the FBI's wiretaps of that Turkish official.

“She got very angry, and later she threatened me and my family's life,” says Edmonds, when she decided not to go along with the plan. “She said, ‘Why would you want to place your life and your family's life in danger by translating these tapes?’”

Edmonds says that when she reviewed Dickerson's translations of those tapes, she found that Dickerson had left out information crucial to the FBI's investigation -- information that Edmonds says would have revealed that the Turkish intelligence officer had spies working for him inside the U.S. State Department and at the Pentagon.

“We came across at least 17, 18 translations, communications that were extremely important for the ongoing investigations of these individuals,” says Edmonds. “She had marked it as 'not important to be translated.'"

What kind of information did she leave out of her translation?

“Activities to obtain the United States military and intelligence secrets,” says Edmonds.

She says she complained repeatedly to her bosses about what she'd found on the wiretaps and about Dickerson's conduct, but that nobody at the FBI wanted to hear about it, not even the assistant special agent in charge.

“He said ‘Do you realize what you are saying here in your allegations? Are you telling me that our security people are not doing their jobs? Is that what you're telling me? If you insist on this investigation, I'll make sure in no time it will turn around and become an investigation about you,’” says Edmonds.

Sibel Edmonds was fired. The FBI offered no explanation, saying in the letter only that her contract was terminated completely for the government's convenience.

But three months later, the FBI conceded that on at least two occasions, Dickerson had, in fact, left out significant information from her translations. They say it was due to a lack of experience and was not malicious.

Dickerson quit the FBI and now lives in Belgium. She declined to be interviewed, but she told The Chicago Tribune that the allegations against her are preposterous and ludicrous. Grassley says he's disturbed by what the Dickerson incident says about internal security at the FBI.

"You shouldn't have somebody in your organization that's compromising our national security by not doing the job right, whether it's lack of skills or whether it's intentional," says Grassley.

Does the Sibel Edmonds case fall into any pattern of behavior, pattern of conduct, on the part of the FBI?

“The usual pattern,” says Grassley. “Let me tell you, first of all, the embarrassing information comes out, the FBI reaction is to sweep it under the rug, and then eventually they shoot the messenger.”

Special agent John Roberts, recently retired as a chief of the FBI's Internal Affairs Department, agrees. And while he is not permitted to discuss the Edmonds case, for the last 10 years, he has been investigating misconduct by FBI employees. He says he is outraged by how little is ever done about it.

“I don't know of another person in the FBI who has done the internal investigations that I have and has seen what I have, and that knows what has occurred and what has been glossed over and what has, frankly, just disappeared, just vaporized, and no one disciplined for it,” says Roberts.

Despite a pledge from FBI Director Robert Mueller to overhaul the culture of the FBI in light of 9/11, and encourage bureau employees to come forward to report wrongdoing, Roberts says that in the rare instances when employees are disciplined, it's usually low-level employees like Edmonds who get punished and not their bosses.

“I think the double standard of discipline will continue no matter who comes in, no matter who tries to change,” says Roberts. “You, you have a certain, certain group that, that will continue to protect itself. That's just how it is.”

Has he found cases since Sept. 11 where people were involved in misconduct and were not, let alone reprimanded, but were even promoted? Roberts says yes.

"That's astonishing," Bradley told Roberts. "You would think that after 9/11, that's a big slap in the face. 'This is a wake-up call here.'"

"Depends on who you are," says Roberts. "If you're in the senior executive level, it may not hurt you. You will be promoted."

Last month, the FBI took the highly unusual step of retroactively classifying information it gave to Congress two years ago about the Sibel Edmonds case.

As for the FBI's language division, the bureau says it has dramatically beefed up its translation capabilities.