Air Force records obtained by The Associated Press show test scores were among the lowest of the year last summer, when dozens of nuclear missile officers allegedly cheated on exams.

But the Air Force isn't saying why that is. It notes that tests are not identical each month, and thus score "variances can be expected."

The facts of the tainted testing are still under investigation by the Air Force Office of Special Investigations. It ranks as the worst such scandal in the history of the intercontinental ballistic missile force and is among a series of security lapses and slip-ups that have plagued the ICBM corps over the past year. The missteps prompted Defense Secretary Chuck Hagel to launch two probes of the entire nuclear force to find root causes for leadership lapses and other problems - steps Hagel deemed necessary to restore public confidence.

Hagel says he believes the nuclear force remains secure and reliable but says "something is wrong."

The alleged cheating has been described as a symptom of mismanagement by commanders who have given too much weight to monthly test scores in determining which launch officers get promoted. More broadly, it reflects a degree of turmoil inside a force responsible for 450 nuclear-tipped Minuteman 3 missiles that stand launch-ready in underground silos in Montana, North Dakota, Wyoming, Colorado and Nebraska.