The hospital where the Marines were sent had been planning a mass-casualty response training for the day of the real-life emergency.
The island of Mindanao has been reeling from the effects of heavy rain, displacing an estimated 795,000 people.
It was an "isolated incident and there was no threat to other Marines or the public,” a Marine spokeswoman said.
Lt. Gen. Roger Turner, whose promotion had been among hundreds blocked by one senator, took over III Marine Expeditionary Force on Friday.
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