Updated

The Navy's top admiral says the service is investigating alleged cheating among senior sailors on written tests related to training on naval nuclear power reactors.

Adm. Jonathan Greenert told a Pentagon news conference Tuesday that he was disappointed in the alleged breakdown in discipline. He said the investigation was ongoing.

The head of the Navy's nuclear propulsion programs, Adm. John Richardson, told reporters that the examinations on which sailors allegedly cheated included classified information.

The allegations involve alleged cheating on tests related to the nuclear reactors that provide propulsion for Navy submarines and aircraft carriers. It does not involve naval nuclear weapons and thus is not directly comparable to the Air Force's investigation of alleged cheating by officers who operate land-based nuclear missiles.

At this stage of the investigation, approximately a dozen sailors are believed to be involved in the alleged cheating, although the investigation is still active and has not reached final conclusions.