As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE NR 3 FIRE LIGHT AND BELL ACTIVATED IN FLIGHT. THE ENGINE THROTTLE WAS REDUCED TO IDLE AND THE WARNING CEASED. WHEN THE THROTTLE WAS INCREASED THE LIGHT CAME ON AGAIN. THE AIRCRAFT WAS RETURNED TO IAH WHERE IT LANDED WITHOUT INCIDENT. MAINTENANCE FOUND THE DUCT FROM 13TH STAGE BLEED TO COWL ANTI-ICE BROKEN. THE DUCT WAS REPLACED AND OPERATIONAL CHECKS WERE GOOD.