The general who commands U.S. nuclear forces said Thursday he has ordered further review of failings discovered among Air Force officers who operate nuclear missiles. But he told Congress on Thursday he was not alarmed by their shortcomings.

Gen. Robert Kehler, commander of U.S. Strategic Command, told a House Armed Services panel that the Air Force assured him it is searching for root causes of the problem among missile launch officers at Minot Air Force Base in North Dakota.

“As I sit here today I don’t see anything that would cause me to lose confidence” in their ability to perform their mission, Kehler said.

A March inspection of the 91st Missile Wing at Minot gave the missile crews the equivalent of a “D” grade in missile operations, leading to revelation Wednesday that the Air Force had removed from duty an unprecedented 17 officers.

Kehler said he has told the Strategic Command’s inspector general to review the results of the Minot inspection, which was performed by the Air Force Global Strike Command. That command is responsible for the missile unit’s training and readiness but would cede responsibility for them to Strategic Command in time of war.

Kehler’s comments stood in contrast to the tone of a confidential email n which a senior officer at Minot sketched a picture of a troubled nuclear unit.

“We are, in fact, in a crisis right now,” Lt. Col. Jay Folds, a deputy commander at Minot, told subordinates April 12. His group is responsible for all Minuteman 3 missile launch crews at Minot.

In his email, Folds lamented the remarkably poor reviews the launch officers received in the March inspection.

Defense Secretary Chuck Hagel responded to the report on Wednesday by demanding more information from the Air Force. The service’s top general, Gen. Mark Welsh, said the problem does not suggest a lack of proper control over the nuclear missiles but rather was a symptom of turmoil in the ranks.

“The idea that we have people not performing to the standard we expect will never be good and we won’t tolerate it,” Welsh said when questioned about the problem at a congressional hearing on budget issues.