The Navy is investigating alleged cheating on a written test by about 30 senior enlisted sailors training to become instructors at the Navy's nuclear reactor school in Charleston, S.C., Pentagon officials said today.

The sailors in question are trained to supervise nuclear reactors and are not involved in the care of nuclear weapons, officials noted.

The news comes on the heels of a cheating scandal at Malmstrom Air Force Base in Montana involving 92 of the 183 nuclear launch officers at the base who care for Minuteman III intercontinental ballistic missiles.

The Navy announced the alleged cheating at the Charleston facility in a hastily arranged Pentagon news conference.

"To say I am disappointed would be an understatement," said Admiral Jonathan Greenert, the Chief of Naval Operations. "The foundation of our conduct throughout the Navy is integrity."

"We expect more from our sailors, especially our senior sailors, and we demand it in our training and in our operations," said the Navy's top admiral.

The investigation involves about 30 of the 150 senior engineering watch supervisors at the Navy nuclear reactor school in Charleston, a Navy official said. These senior enlisted sailors have already operated nuclear reactors during submarine deployments but have to be re-certified to become instructors at the school.

Working in 11-man teams, they also provide 24-hour maintenance for the nuclear reactors aboard two decommissioned submarines that are used for training.

Admiral John Richardson, the head of the Naval Nuclear Propulsion Program, said the allegations of cheating involve a "written exam to qualify just one of those 11 watch stations, one of the 11-person team."

The sailors implicated by the allegations have been removed from their posts and had their access revoked, officials said.

The Navy announced the allegations less than 24 hours after a sailor told commanders about being approached to join in on the cheating for the test, officials said.

The reactors were shut down for regular maintenance at the time that the cheating was first reported Monday, Richardson said, noting they will not be re-started "until I am personally satisfied that appropriate corrective actions have been taken and additional conservative measures have been implemented."

The two admirals expressed confidence in the safety of the Navy's nuclear reactors, noting there are several layers of testing for the sailors charged with their care and maintenance.

As a precautionary measure, all qualified instructors not implicated by the allegations are also being re-tested, officials said.