What was found
CREW OBSERVED BURNED PLASTIC ODOR IN CABIN. EMERGENCY DECLARED AND RETURNED TO PIT WITHOUT FURTHER INCIDENT. GROUND RAN AIRCRAFT WITH BOTH AIR CONDITIONING PACKS ON HIGH. INSPECTED E/E BAY, CARGO BAYS, AFT ACCESSORY COMPARTMENT, AND BOTH MAIN LANDING GEAR BAYS. CHECKED CABIN LIGHTS BALLASTS. CHECKED LAVATORIES AND TRASH BINS. UNABLE TO DUPLICATE. SYSTEM GROUND CHECKED NORMAL OPERATION. (M)