The plane lost radio contact shortly after 6 p.m. Officals later said it had crashed.
A Chilean Air Force plane flying to Antarctica with 38 people on board crashed on Monday afternoon, officials said.
The C130 Hercules, which took off from the city of Punta Arenas, was flying to President Eduardo Frei Montalva Antarctic Air Base when it disappeared, Chile's Air Force said in a statement.
The plane, which was transferring personnel to a floating fuel supply pipeline, lost radio contact shortly after 6:00 p.m. Officials later said it had crashed.
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Twenty-one people aboard the plane were passengers and 17 were crew members, the statement said.
President Sebastian Piñera said authorities were monitoring search and rescue efforts.
This is a developing story.