The Chilean military transport plane was flying over the notoriously treacherous Drake Passage when contact was lost.
Debris believed to be from a missing Chilean air force plane that had 38 people on board has been found, officials have said.
The C-130 Hercules jet, which was carrying 17 crew members and 21 passengers, went missing less than two hours after taking off from the southern city of Punta Arenas on Monday afternoon.
General Eduardo Mosqueira announced on Wednesday that a “sponge” material had been found floating in the water about 30km from the last known location of the plane, which was en route to Antarctica.
Analysis of the debris will take a few days before its origins can be confirmed, but the general said it could be from the plane’s internal fuel tanks.
Searches will continue in the meantime, with teams scanning an area of roughly 70,000 square miles using planes, satellites and ships, including vessels from Argentina, Brazil, Uruguay and the US.
It covers much of Drake Passage, located between the tip of South America and Antarctica.
Ed Coleman, a pilot and expert from Embry-Riddle Aeronautical University in Arizona, said the route was treacherous because of rapidly changing weather in the Antarctic.
He explained: “You can have a clear sky one minute, and in a short time later storms can be building up making it a challenge, which causes bigger swells and rougher air.”
The conditions will be just as dangerous for the search and rescue teams, he added.