WASHINGTON — 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, who is a Butler native, 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.