Argentina says a sound detected in the missing submarine search is consistent with an explosion.
The noise was observed around the time the ARA San Juan submarine sent its last signal last week.
Navy spokesman Enrique Balbi described the blast in the morning of 15 November as “abnormal, singular, short, violent” and “non-nuclear.”
It was “consistent with an explosion”, he added.
The navy did not have enough information to say what the cause of the explosion could have been or whether the ARA San Juan could have been attacked, Balbi told reporters.
A huge sea and air hunt is being conducted for the craft, which went missing with 44 crew on board.
The disappearance has plunged relatives of the crew members into an anguished wait for news and transfixed the South American country.
The information about the explosion received on Thursday morning was consistent with a separate report received on Wednesday of an “acoustic anomaly” in the same area and around the same time the vessel gave its last signal, Balbi said.
“This is very important because it allows us to correlate and confirm the acoustic anomaly from the US report yesterday,” he said.
The site of the abnormal sound was close to where the German-built vessel gave its last location, about 430 km off the coast.
Earlier on Thursday, a US embassy spokeswoman said an object detected by a US Navy plane near the area where the submarine sent its last signal turned out not to be the missing vessel.
On Thursday it also emerged that an international nuclear test-ban body that runs a global network of listening posts designed to check for secret atomic blasts detected an “unusual signal” last week, close to where the submarine went missing.
The Vienna-based Comprehensive nuclear Test-Ban Treaty Organisation (CTBTO) runs monitoring stations equipped with devices including hydrophones - underwater microphones that scan the oceans for sound waves.
CTBTO engineer Mario Zampolli said: “It could be consistent with an explosion but there is no certainty about this.”
Concerns are growing that the submarine could be near the last of its seven-day oxygen supply.
Relatives of the crew members have gathered at a naval base in the coastal city of Mar del Plata, some 400 km south of Buenos Aires, where the search is being coordinated.
The submarine was en route from Ushuaia, the southernmost city in the world, to Mar del Plata when it reported an electrical malfunction shortly before disappearing last week.
The submarine was launched in 1983 and underwent maintenance in 2008 in Argentina. Its four diesel engines and its electric propeller engines were replaced, according to specialist publication Jane’s Sentinel.