Robert Mueller will inherit a dizzying array of inquries when he takes over as Head of the FBI on Sept. 4.

WASHINGTON (AP) - The FBI is under the microscope, facing a barrage of investigations into everything from alleged threats against whistleblowers to lost weapons.

It's quite a switch for an agency that is used to doing the investigating and operates largely in secret. The scrutiny is coming from all directions. Congress, the Justice Department and outside experts are looking into a series of bungles that have dogged the FBI in recent years.

FBI officials say the bureau is cooperating fully with investigators.

"While it's a significant burden, FBI employees understand the need for this oversight and at the same time are fulfilling their law enforcement and national security responsibilities," said spokesman Mike Kortan.

The scrutiny and a steady stream of headlines extolling the latest blunder have taken a toll on morale, observers say.

"It's something very different from what they are accustomed to," said Michael Bromwich, a former Justice Department official who investigated problems with the FBI laboratory. "The spotlight is on the FBI."

FBI officials were bracing for the release Monday of portions of a review highly critical of the bureau's handling of the Wen Ho Lee case.

Lee, who had worked on top-secret nuclear weapons programs since the 1970s, was indicted on 59 felony charges alleging he transferred nuclear weapons information to portable computer tapes. He spent nine months in solitary confinement, but all but one charge against him was eventually dropped.

At least six other investigations into the FBI under way. Officials confirmed last week that the Justice Department's Office of Inspector General, an internal watchdog, is investigating allegations of retaliation against agents assigned to look into the bureau's handling of the 1992 standoff with white separatists in Ruby Ridge, Idaho.

As part of the inquiry, Inspector General Glenn Fine is looking into allegations that senior FBI officials are immune from disciplinary measures and punishments imposed on lower-ranking agents.

The Senate Judiciary Committee also is scrutinizing an alleged double standard that protects top managers from punishment.

Lawmakers are especially interested in whether the FBI's Office of Professional Responsibility, which for years had primary responsibility for investigating wrongdoing at the bureau, helped foster a double standard.

Robert Mueller, the newly installed FBI director, said the bureau would admit its mistakes, correct them and hold agents and senior officials accountable under his leadership.

He'll inherit a dizzying array of inquries when he takes over Sept. 4.

The inspector general is also investigating:

-The FBI's performance in detecting and investigating Robert Hanssen, a veteran agent who has admitted spying for Russia

-Why the FBI failed to turn over documents to lawyers for Oklahoma City bomber Timothy McVeigh. That incident forced Attorney General John Ashcroft to postpone McVeigh's execution nearly a month.

-How the FBI keeps track of weapons, laptops and other equipment following the FBI's disclosure that hundreds of guns and computers are missing. One gun was used in a murder.

Not all of the inquiries have gone smoothly. Fine's investigators initially encountered problems obtaining documents from the FBI early in the Hanssen investigation, said sources familiar with the probe, speaking on condition of anonymity. They said the bureau now is cooperating.

Meanwhile, a commission headed by former CIA and FBI director William Webster is investigating the Hanssen matter and the Justice Department has hired consulting firm Arthur Andersen LLP to study the FBI's management structure.

All of these findings will be reviewed by a team of top Justice Department officials who are doing their own assessment of the FBI and will make recommendations to Ashcroft about how to best overhaul the bureau.