Updated

U.S. Navy investigators have dismissed allegations that pervasive cheating tainted training exams administered to enlisted sailors and officers in the submarine force, according to documents obtained Thursday by The Associated Press.

The inspector general for the Atlantic submarine force opened an investigation following a complaint that originated in Groton, Conn., the home port of an attack submarine that was hit by a cheating scandal in 2010.

In a letter sent to U.S. Fleet Forces Command in December, the commander for the Atlantic submarine force said the claims were unsubstantiated. It said previous episodes mentioned in the complaint were investigated and dealt with individually.

The letter, which the AP obtained through a Freedom of Information Act request, recommended the case be "closed as unsubstantiated with no further action."

The investigation began with a complaint from a crew member aboard the USS Memphis, a submarine that lost about 10 percent of its crew to disciplinary measures after a cheating ring was discovered in November 2010. The crew member also complained that the punishments were unduly harsh and influenced by abuse of authority -- claims that were also investigated and dismissed by the Navy.

The Navy has insisted that the episode reflected a rare lapse in integrity. But some former officers told the AP that it was an extreme example of shortcuts that sailors on other submarines have taken to pass increasingly difficult nuclear training exams that have little bearing on skills sailors actually need.

The unidentified crew member who filed the complaint said his punishment was unfair because so many others got away with cheating.

"He equated it to 'doing 60 in a 55 and instead of a speeding ticket we lost our license for life,"' the Navy report said.

In the case of the Memphis, sailors were emailed the answers before qualification exams, took tests outside the presence of proctors and openly asked officers for answer keys. The cheating episode was among the lapses mentioned by the commander of the Navy's submarine force, Vice Adm. John Richardson, in a blog posting last month stressing the importance of character.

"Invisibility and character have a long relationship, and it hasn't always been a healthy one. Being out of sight can uniquely challenge one's character," he wrote.

Navy leaders have been tracking the allegations of widespread cheating.

In a September 2010 email, Adm. Kirkland Donald, director of naval reactors, alerted the chief of naval operations to cheating allegations included in a book by former submarine officer Christopher Brownfield. Donald said there had been several noteworthy "busts" among nuclear operators, and the Navy followed up in each case with "strong accountability measures." But he said integrity remained a focus.

"I wish I could tell you that we solved the problem, but we still have occasional events that indicate that we haven't," Donald wrote in the email, which was obtained by the AP. "I assure you that this matter has my full attention and energy."

Donald's office did not immediately respond to a request for comment.

Brownfield, who described cheating aboard the USS Hartford submarine in his book, said he has never been contacted by naval investigators about the cheating allegations. He questioned the Navy's dedication to get to the bottom of the issue.

"They say they're taking it seriously, but they don't contact the person who's making the allegations," said Brownfield, who is now studying alternative energy at Columbia University.

He said investigators might also have overlooked some examples because the cheating often was not overt, more often involving subtle hints and dropped clues.

"There was a lot of room for gray area on it," he said. "People might not have considered it cheating."