When the federal government considers information too sensitive to be released to the public, it must have a good reason. And no reason is of greater import than national security.

That’s why the investigation into the leak of classified information in 2002 must be taken seriously, and it’s why U.S. Sen. Richard Shelby, a Republican from Tuscaloosa, whose office is one object of the investigation, is right in cooperating fully with the Justice Department.

Here’s what we know:

On or just before Sept. 10, 2001, the National Security Agency intercepted two messages indicating that something was about to happen the next day. That would have been Sept. 11, 2001.

The messages were not translated until Sept. 12, but even then they were ambiguous. They did not indicate what would happen or when, where or how.

Of course, it’s purely speculative as to whether the information could have prevented the Sept. 11 terrorist attacks on New York and Washington. Such messages are probably intercepted daily and have been for years. Some have grave meaning, others have none at all.

But the fact that such messages existed was classified, an especially important fact as congressional investigations into the attacks continued into the next year.

Then, on June 19, 2002, CNN, citing “congressional sources,” reported the fact that the messages were intercepted and portions of their contents. One phrase used was “the match begins tomorrow.”

CNN’s report spurred a Justice Department investigation. Within two months, the FBI had questioned more than 100 people, including all 37 members of the Senate Intelligence Committee, of which Shelby was then chairman, and some 60 staff members. Schedules, calendars and phone records were obtained. The CNN reporter was also interviewed.

This week, The Washington Post reported that the FBI investigation has focused on the office of Sen. Shelby. In a statement, Shelby said that neither he nor anyone else in his office had knowingly compromised classified information. He pledged his continued cooperation, but he noted that he had not been contacted about the investigation for more than a year.

Given the fact that the information is still classified and the fact that the investigation must be conducted out of the spotlight, there is little more that Shelby can or should say. The probe must go where the evidence leads, and those involved must simply wait.

At some point, the American people deserve to know everything the government knew and when the government knew it. Even so, the public must give investigators some latitude. Citizens cannot allow incriminating information to be shoved under the rug, but they should not drag it out prematurely, either. The people must be patient, which can be difficult in a society where people expect instant gratification and instant answers.

For now, we take Shelby at his word, that neither he nor anyone else on his staff knowingly compromised classified information. To suggest otherwise would be to question their loyalty, and there is no basis for doing so. When the facts come out, they will almost certainly prove that whoever leaked the information – on Shelby’s staff or someone else’s – showed poor judgment, not a disregard for the security of their fellow citizens.

That’s the presumption every American should be entitled to. That’s the presumption that must apply in this case as well.