That bureau now has a construction industry task force pursuing a wide range of possible wrongdoing.
Executive privilege cannot be used to conceal a crime or a possible wrongdoing.
The four are being investigated by the Justice Department for possible criminal wrongdoing.
About 4,000 former bank officials are under investigation for possible financial wrongdoing.
Unlike other investigations of possible wrongdoing, he said, "this one has already been tried and decided in the public press."
Not only the issue of the administration's possible wrongdoing is important.
They were often sent out into the provinces to investigate possible wrongdoing on the part of local officials.
Their mission is to spot and report possible wrongdoing, leaving enforcement to the authorities.
An Army official said inquiries were made into more than 60 cases of possible wrongdoing.
It is not clear what possible criminal wrongdoing may have led to the investigation.