What was found
ACFT WAS DISPATCHED TO A FIRE. MADE (3) WATER DROPS AND WERE RELEASED. ACFT LANDED AT REMOTE FUELING SITE WITHOUT INCIDENT. REFUELED AND ONE HOUR LATER WAS DISPATCHED TO ANOTHER FIRE. ACFT WAS STARTED AND RUN-UP NORMALLY. JUST PRIOR TO LIFT-OFF PIC NOTICED MAIN GEAR BOX CHIP LIGHT WAS ILLUMINATED. THE ACFT WAS SHUTDOWN. MECHANIC PULLED CHIP DETECTOR AND FOUND METAL. PULLED MGB FILTER SCREEN FOUND TO BE FILLED WITH METAL. ACFT WAS GROUNDED FROM FURTHER FLIGHT. TRANSMISSION WILL BE SENT FOR TEARDOWN, TO DETERMINE CAUSE OF METAL CHIPS.