As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
10 MINUTES INTO THE FLIGHT, FIRE WARNING AUDIO WAS HEARD FOR A SHORT PERIOD OF TIME IN THE HEADSET. AIRCRAFT WAS RETURNING TO DEPARTURE LOCATION AND THE AUDIO WAS HEARD ONCE MORE FOR A SHORT PERIOD OF TIME. NO LIGHTS ILLUMINATED ONLY AUDIO SOUND.