The CBI on Tuesday filed its first charge sheet in the alleged leak of sensitive information on submarine retrofitting projects against six persons including two serving naval officers, officials said.

This is one of the quickest probes in defence corruption cases as the agency filed the charge sheet within 60 days of the first arrests made on September 3 to ensure that the arrested accused do not get easy bail.

The CBI has to file a charge sheet within 60 days of arrest of accused in corruption case else they become eligible for bail. The limit is special crime cases is 90 days.

In its charge sheet filed before a special CBI court at Rouse Avenue, the CBI slapped section 120-B (criminal conspiracy) of Indian Penal Code and provisions of Prevention of Corruption Act.

The case began when the agency received the input that some serving officers in the Western Headquarters of Navy working on retrofitting of Russian Kilo class submarines were allegedly being influenced by retired naval officers and were receiving pecuniary benefits, the officials said.

After registering a case on September 2, the CBI carried out searches the next day during which two retired officers Commodore Randeep Singh and Commander SJ Singh, who works for a Korean Submarine company, were arrested, they said.

During further searches, the CBI claimed to have recovered Rs 2 crore from the residence of one of the retired Navy officers.

Later during the probe, the CBI took into custody a serving Navy officer Commander Ajeet Kumar Singh, and another Commander working with him, they said.

An alleged hawala dealer and director of a private company were also taken into custody during the probe, officials said.

It is alleged that the serving officers were allegedly leaking confidential information to their retired officers in return for pecuniary gains.

Sources said further probe is continuing and the role of some foreign nationals is also under scanner.

The Anti-Corruption Unit of the agency, which handles sensitive and high profile corruption cases, was tasked to unearth the leakage of information following which the operation was started, they said.

The unit has questioned several other officers and ex-servicemen who were in regular touch with the arrested officer and retired personnel, they said.

The CBI is conducting a forensic analysis of digital products used by the officer to understand if the information had fallen into the hands of people with vested interests, they said.

"Investigation related to alleged information leak of administrative and commercial nature being with some unauthorised personnel has come to light and is being investigated by appropriate government agency," the Navy had said in a statement.

The investigation by the agency with complete support of the Indian Navy is in progress, it had said.

An internal inquiry by the Navy is also being progressed, it had said.