Answering written queries in Lok Sabha, Defence Minister A K Antony said three Navy officers have been dismissed from service in May this year for sharing information through emails.
"The loss of Defence Services Staff College 2012 answer books in attributable to the negligent handling of mail bags in transit by Air India," he said.
The Defence Minister denied that there was any "counter terrorism" angle involved in the case.
Antony said the affected officers have been given an opportunity to appear for a re-test which was conducted in December last year.
Also Read
The answer sheets of the exam conducted in September last year at the Missamari centre had gone missing in transit.
Answering another query, the Defence Minister said 15 incidents of bullying and ragging have been received from various military and sainik schools across the country.
On the naval issue, he said in September 2011, a case had come to light where four naval officers were found blameworthy for unauthorised sharing of information through personal email accounts.