As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EWR CREW REPORTED FIRE WARNING FROM FWD CARGO COMPARTMENT. BOTTLES WERE DISCHARGED & WARNING WENT OUT BUT RETURNED. EMERGENCY DECLARED FLIGHT RETURNED EWR LANDED WITHOUT INCIDENT. ACFT REMOVED FROM SERVICE. FOUND NO SIGNS OF FIRE. REPLACED CARGO FIRE BOTTLE, MPN 4739574. REPLACED A1 DETECTOR AT LGA ON 03/18/2014. SYS GND CHECKED NORMAL OPERATION CLOSED.