An American in the United States Antarctic Program was recently evacuated from Antarctica and admitted to a New Zealand hospital in serious condition, officials said.

The individual was transported from the U.S. McMurdo Station for emergency medical treatment on July 31, in an operation carried out under “dangerous” winter conditions, according to the U.S. National Science Foundation, which manages the Antarctic program.

The Australian Antarctic Division, a government group that leads Australia’s Antarctic Program that assisted in the medical evacuation, confirmed that the rescue was of an American citizen. 

The expeditioner was admitted to Christchurch Hospital in serious condition, according to the U.S National Science Foundation. No additional details on the individual have been released.

The U.S National Science Foundation said it requested assistance from the Australian Antarctic Division and the New Zealand Defense Force to transport the individual for emergency medical treatment.

An Australian plane made the five-hour trip from Hobart, arriving at McMurdo Station in “complete darkness,” the Australian Antarctic Division said.

“With temperatures dipping as low as −43°C and conditions deteriorating, the crew transferred the patient onto the plane and flew to Christchurch,” the division said in a statement on Friday.

The U.S. National Science Foundation said it is grateful to the first responders who provided emergency medical care and “our Australian and New Zealand partners for their life-saving transportation support in dangerous Antarctic winter conditions.”