A Chilean Air Force plane heading for Antarctica with 38 people on board is presumed to have crashed into the ocean after all contact was lost, local officials say. A search-and-rescue operation is underway but there was no immediate sign of the wreckage.

The C-130 Hercules aircraft had taken off from Punta Arenas in southern Chile at 4:55 p.m. local time on Monday. Contact was lost more than an hour later, at 6:13 p.m., when the transport plane was flying over Drake Passage, which connects the Pacific Ocean and the Atlantic Ocean.

A statement from the Chilean Air Force said the plane was heading to Base Presidente Eduardo Frei Montalva, which is located on King George Island, off the coast of Antarctica. A total of 38 people were on board, including 21 passengers and 17 crew members.

“The aircraft was carrying out logistical support tasks, transferring personnel for the revision of the floating fuel supply pipeline at the base and for carrying out anticorrosive treatment of national facilities in the area,” the air force said in a statement.

Officials said the plane was presumed to have crashed into the ocean because there was no sign of the aircraft by 12:40 a.m., at which time the plane would have run out of fuel. A search and rescue operation was continuing on Tuesday morning.

The identities of those on board the plane were not immediately known, but most or all of them are believed to be citizens of Chile. Of the 21 passengers, 15 are members of the air force, 3 are members of the army, and 3 are civilians. This includes 2 employees of INPROSER and 1 from the University of Magallanes.