The Central Bureau of Investigation (CBI) has arrested a Commander-rank serving officer and two retired officials of the Indian navy along with two other persons for allegedly leaking confidential information related to an ongoing submarine project in lieu of illegal gratification, people familiar with the development said on Tuesday.

The federal anti-corruption probe agency refused to divulge any other details of the case, including the name of the serving officer arrested for the leak.

However, officials who didn’t want to be named said the secret action was initiated last month and the matter relates to the upgrade of Russian-origin Kilo class submarines in the Indian fleet.

At least 19 locations in Delhi, Mumbai, Noida and Hyderabad have been raided so far in the case and several people as well as recovered digital evidence are being examined.

It is alleged that the Commander had discussed crucial details about the ongoing modernisation project of Kilo class submarines with the two retired officers for alleged illegal gratification, said an official.

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 added.

Investigation is being carried out to unearth if the information has fallen into the wrong hands.

The Indian Navy said on Tuesday that 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 investigation by the agency with complete support of the Indian Navy is in progress, it added.

An internal inquiry by the Navy is also underway and is being carried out by a vice admiral to find out how information leaked despite security protocols and advisories, and how lacunae, if any can be fixed, officials said.

India operates eight Kilo class submarines, four HDW German origin submarines and three Scorpene submarines built in India under technology transfer from France (three more Scorpenes will join the fleet in the future). The navy also operates an indigenous nuclear-powered ballistic missile submarine, INS Arihant.

India is also pursuing a project worth ₹43,000 crore for building six advanced submarines in the country under the government’s “strategic partnership” (SP) model to bolster the Indian Navy’s underwater force levels and counter the rapid expansion of China’s submarine fleet. The new submarines are part of the 30-year submarine-building programme approved by the Cabinet Committee on Security in 1999.