Making a statement in the Upper House of the Parliament, Antony said, "Preliminary investigations indicate that the explosion was due to the possible ignition of armament."
Antony, however, said the cause of ignition is yet to be established.
"The cause of ignition is, however, yet to be established. Visual and forensic examination would throw more light into the possible cause of ignition," Antony said.
"Initial assessments indicate that an internal explosion occurred in the forward compartment of the submarine where ordnance was stowed, resulting in further near-simultaneous explosions and major fire on board INS Sindhurakshak," he said.
The defence minister said a forensic investigation, required to ascertain the cause, will be possible only "after the submarine is afloat and dewatered."
"A Board of Inquiry with all relevant specialists has been constituted to investigate the likely causes of the accident at the earliest," Antony said.
Speaking about the 18 naval personnel, including three officers, and 15 sailors who could not evacuate from the submarine, Antony said conditions indicate the "personnel would not have survived."
Offering his condolences to the kins of the victims, he said a special family cell has been formed in Mumbai for their assistance.
Meanwhile, the rescue divers of the Indian Navy on Monday recovered the seventh body, out of the 18 personnel feared killed, from the wreckage of INS Sindhurakshak submarine that sank after an explosion on the intervening night of Tuesday and Wednesday in Mumbai.
The body has been taken to state-run JJ Hospital for autopsy, media reports said.
The Indian Navy on Friday released the names of 18 crewmen who were on board INS Sindhurakshak.
There were three officers and 15 sailors on the vessel.
The three officers were Nikhilesh Pal, Alok Kumar and R Venkitaraj.
The 15 sailors were Sanjeev Kumar, KC Upadhya, Timothy Sinha, Kewal Singh, Sunil Kumar, Dasari Prasad, Liju Lawrence, Rajesh Tootika, Amit K Singh, Atul Sharma, Vikas E, Naruttam Deuri, Malay Haldar, Vishnu V and Seetaram Badapalli.
In a major setback to the Navy's ambitious modernization drive, the fully armed INS Sindhurakshak, returned by Russia earlier this year after a major refit at an estimated cost of USD 80 million, exploded in a Mumbai dock.
--IBNS (Posted on 19-08-2013)