“Despite the magnitude of the efforts made, it has not been possible to locate the submarine,” navy spokesman Enrique Balbi said on Thursday.
The sub, the ARA San Juan, last made contact on Wednesday 15 November.
Hopes of finding survivors faded after a suspected explosion was reported near its last-known location.
Capt Balbi said the search for the submarine had been “extended to more than double the number of days that determine the possibilities of rescuing the crew”.
His comment refers to the estimated period that it is thought the crew could have survived in the submerged vessel.
Capt Balbi said that despite not being able to confirm the fate of the crew, “no evidence of a shipwreck was found in the areas explored”.
He said that the “phase had changed” and that the operation, involving numerous vessels and other submarines, was now a hunt for a wreck on the seabed in the area where the ARA San Juan is believed to have vanished.
The ARA San Juan was returning from a routine mission to Ushuaia, near the southernmost tip of South America, when it reported an “electrical breakdown”.
According to naval commander Gabriel Galeazzi, the submarine surfaced and reported what was described as a “short circuit” in the vessel’s batteries.
The sub was ordered to cut its mission short and return to the naval base in Mar del Plata immediately.
The Argentine navy’s last contact with the vessel was at approximately 07:30 (10:30 GMT) on 15 November, at which point its captain had reportedly confirmed that the crew were well.
Eight days after the sub vanished, the Vienna-based Comprehensive Nuclear Test-Ban Treaty Organisation said that it had detected a noise a few hours after the sub’s last contact.
The body, which operates a network of listening posts to monitor nuclear explosions, said that there had been a “hydro-acoustic anomaly” about 30 nautical miles (60km) north of the sub’s last-known position at 10:31 (13:31 GMT).
The Argentine navy said it could have been the sound of the submarine imploding.
On Tuesday, Capt Balbi told reporters that water had entered the submarine’s snorkel, which can be used to take in air from above the surface when the submarine is submerged.
The saltwater dripped onto a battery tray in the prow, causing the battery to short circuit and to smoulder, he said.
News of the suspected explosion on board the ARA San Juan was last week broken to relatives of the missing crew gathered at the Mar del Plata navy base, who responded with anger and tears.
Some family members accused the navy of lying to them and of raising false hopes.
Others pointed the finger at the government, saying a lack of investment coupled with corruption in the armed forces had made the submarine unsafe. (Courtesy BBC)