The first evacuation flight carrying U.S. citizens has left Japan, the U.S. State Department said on Thursday, following the radiation threat sparked by the crippled nuclear plant.

The flight carried about 100 passengers, including family members of U.S. diplomats and private citizens, said Under Secretary of State Patrick Kennedy.

He said at least another aircraft will be provided on Friday for evacuation.

The U.S. State Department on Wednesday had authorized the voluntary departure for family members and dependents of U.S. government officials who wish to leave Japan. It has also issued a travel warning urging its citizens to defer visit to Japan.

U.S. Nuclear Regulatory Commission recommended on Wednesday that U.S. citizens who live within 50-mile (80-kilometer) radius of the quake-hit Fukushima Daichi nuclear power plant evacuate from that area.