An investigation by the US naval office into the disappearance of Argentinian submarine ARA San Juan has revealed that the vessel imploded and sank at a speed of between 10 and 13 knots, killing all 44 crew immediately.

"The acoustic signal that originated... on November 15, 2017, was caused by the collapse (implosion) of the pressure inside the ARA San Juan at a depth of 388 meters, the energy that the collapse released was equivalent to the explosion of 5,669 kilograms of TNT (explosives)," the report reads.

The submarine disappeared from radars on November 15 and, according to the US Office of Naval Intelligence, the acoustic signal that was detected that same day came from the vessel.

The report adds that under those conditions the San Juan's hull was completely pulverized "in 40 milliseconds", so the crew did not suffer.

"They did not suffer or drown, their death was instantaneous," the report says. The Argentine Navy has yet to comment.

--Bernama-NNN-EFE