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Two support workers at the main United States research base in Antarctica died Wednesday in an accident at a generator building, the National Science Foundation said.

The victims were fire technicians employed by PAE, a contractor based in Arlington, Va., that provides logistical and technical support in Antarctica and elsewhere. The foundation, a federal agency that runs the United States program in Antarctica, did not make public information about the victims but said their next of kin had been notified.

Emails and phone calls to PAE on Thursday morning were not immediately returned.

The foundation said the workers had been doing routine maintenance on a fire-suppression system at the building, at Mount Newall in the Dry Valleys. The generator it houses powers a radio transmitter. Mount Newall is about 60 miles from McMurdo Station, which is on Ross Island in the Ross Sea.

A helicopter pilot lower down the mountain who was waiting to take the technicians back to McMurdo became concerned when they did not return to the aircraft at the appointed time. He hiked up to the building and found the two workers unconscious inside on the floor. One was dead at the scene; the other was flown to McMurdo’s medical clinic and was pronounced dead a short time later.