Australia's The Australian newspaper on Thursday uploaded a fresh tranche of leaked documents relating to information about operating instructions of underwater warfare system of the six Scorpene submarines which are being built in India by French firm DCNS.
However, a top defence analyst allayed fears that it could compromise the security of the strategically important combat vessels.
Like in the previous case, the newspaper has blacked out all details which it felt would compromise India's security interests.
However, the new set of documents, with Indian Navy insignia on it and marked "Restricted Scorpene India", gives details about the sonar system of the submarines which is used to gather intelligence underwater.
It talks about a wide range of technical specifications of the sonars and at what degree and frequency it will function. It has a System Technical Manual and an Operating Instruction Manual that have crucial details of the combat management system
The documents detail the "Operating Instruction Manual", which talks about how to select a target for weapon firing, weapon configuration selection, among others.
While the vital parameters and exact details have been redacted or blacked out, the original documents contain all data.
These details may be put together and make detecting the submarine easier.
The document even gives out the frequency band of the Sonar intercept receiver, distributed array, active array.
Indian Navy has so far maintained that the details would not reveal the final submarine's signature, as the specifications in the document are generic and each boat has a unique signature that is known only when it is ready and in the waters.
The total leaked documents run over 22,000 pages.
The first set of documents uploaded by "The Australian", included technical manuals of the boat, as also details like its acoustic signature and levels of noise radiation.
Tracking a submarine involves sophisticated sonar equipment that can detect, classify, locate and track a vessel based on echoes from its hull and the noise it generates.
Hull reflection, radio and radar signals and water pressure can also give away a submarine's location.
To this extent, the Scorpene's stealth characteristic is its biggest strength. This has been achieved by modifying its hull and reducing its noise footprint.
Though the Navy has not yet officially reacted to the release of new documents, sources maintained that it does not compromise national security.
They said the same information about a submarine was on many naval defence websites.
"On the face of it, these documents are basic operating manual. You buy any goods from the market, it will come with an operating manual," defence analyst Commodore Uday Bhaskar (Retd), Director of Society of Policy Studies told PTI.
"If the question is whether tonight's revelation has made our submarines vulnerable, then the answer is no," he said.
"It is more like basic operating instructions for the user," he said.
The paper said it has been told that the secret data was removed from DCNS by a former sub-contractor in 2011 and taken to a private company in Southeast Asia before being passed on to a branch of that company in a second Southeast Asian nation.
A disk containing the data filed was then posted in regular mail to a company in Australia.
DCNS is focusing its investigation on former employees and sub-contractors involved in the project. At this stage it is not thought that the leak came from India.