The international effort to find a missing Argentinian submarine has come up empty after scouring more than two-thirds of the search area, the navy spokesman said Wednesday.

The final contact with the ARA San Juan, which had 44 crew members aboard, was on November 15.

Two weeks later, the search is focused on a patch of the South Atlantic about 40 square kilometers (15 square miles) around the point of the explosion that likely doomed the vessel, as well as calculations based on the sub's direction and speed, Argentina's navy spokesman Enrique Balbi told reporters.

Aircraft and ships from 18 countries looking for the submarine have already covered 68 percent of the search area, Balbi said.

The search is taking place about 450 kilometers (279 miles) off Argentina's southern coast, in an area where the depth of the ocean floor varies between 200 and 1,000 meters.

Balbi said it was hard to tell when the ships and planes will have covered all of the search area. "It depends on the weather," he said. "It is a slow sweep."

Weather conditions will be favorable on Wednesday and Thursday, Balbi said, adding that at least eight ships are operating in the search area.

In their last message, the submarine crew reported an electrical short-circuit caused by sea water which had started a fire, an Argentinian TV channel reported on Monday.

The submarine said sea water had entered the ventilation system, causing a battery on the diesel-electric vessel to short-circuit and start a fire, according to the text of the message, which was reported by the A24 television channel.