Narrative:

At approximately XA10 pm; my crew and I were operating flight xx from ZZZ to ZZZ1. In addition to us there were 4 passenger on the flight; seated in the rear area of the cabin. Approximately 10 mins after departure we observed the smoke warning light illuminate for a total of approximately 5-8 seconds; and then extinguish. No smoke or fire was observed. We subsequently donned our oxygen masks and goggles; declared an emergency with ATC; and began a return to ZZZ. We executed the appropriate emergency checklists; in the process communicating the situation to the flight attendant. She subsequently informed us that no fire or smoke was present in the cabin; and no heat or evidence of fire was apparent upon examining the baggage compartment access door. We landed at ZZZ and taxied to the gate with the fire equipment standing by. After deplaning the passenger; we inspected the aircraft with the fire crew and discovered no evidence of fire or smoke. In investigating the source of the indication the flight attendant had asked the passenger if their cell phones were on; they responded in the negative. However; the flight attendant said at the time that she had observed a passenger seated in the aft of the aircraft text-messaging on a cell phone earlier during taxi; and though she subsequently directed the passenger to turn off all electronic devices; she later expressed reasonable suspicion that this individual might not have complied with her instructions. I made telephone contact with dispatch and maintenance. I communicated our entire situation to the mechanic on duty. I also explained our suspicion about the cell phone. He agreed with that possibility of cell phone interference and responded by saying that we should perform the baggage smoke warning system test; and that if the system test was successful that we would be clear to continue the flight. I performed the test as directed in the first flight/post maintenance checklist; and the system tested normally. I then communicated that information to dispatch. Our collective decision; based on communication with maintenance; was that the system was functioning normally and no maintenance write-up was required. Dispatch then released us to continue the flight. Upon reboarding the passenger; we thoroughly explained the situation to them; and requested that they please ensure all cell phones remained off for the duration of the flight. We subsequently continued to ZZZ1 without further incident.

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Original NASA ASRS Text

Title: A DASH 8 FLT CREW RECEIVED A SMOKE WARNING LIGHT; DECLARED AN EMERGENCY AND RETURNED TO DEPT ARPT.

Narrative: AT APPROX XA10 PM; MY CREW AND I WERE OPERATING FLT XX FROM ZZZ TO ZZZ1. IN ADDITION TO US THERE WERE 4 PAX ON THE FLT; SEATED IN THE REAR AREA OF THE CABIN. APPROX 10 MINS AFTER DEP WE OBSERVED THE SMOKE WARNING LIGHT ILLUMINATE FOR A TOTAL OF APPROX 5-8 SECONDS; AND THEN EXTINGUISH. NO SMOKE OR FIRE WAS OBSERVED. WE SUBSEQUENTLY DONNED OUR OXYGEN MASKS AND GOGGLES; DECLARED AN EMER WITH ATC; AND BEGAN A RETURN TO ZZZ. WE EXECUTED THE APPROPRIATE EMER CHKLISTS; IN THE PROCESS COMMUNICATING THE SITUATION TO THE FLT ATTENDANT. SHE SUBSEQUENTLY INFORMED US THAT NO FIRE OR SMOKE WAS PRESENT IN THE CABIN; AND NO HEAT OR EVIDENCE OF FIRE WAS APPARENT UPON EXAMINING THE BAGGAGE COMPARTMENT ACCESS DOOR. WE LANDED AT ZZZ AND TAXIED TO THE GATE WITH THE FIRE EQUIP STANDING BY. AFTER DEPLANING THE PAX; WE INSPECTED THE ACFT WITH THE FIRE CREW AND DISCOVERED NO EVIDENCE OF FIRE OR SMOKE. IN INVESTIGATING THE SOURCE OF THE INDICATION THE FLT ATTENDANT HAD ASKED THE PAX IF THEIR CELL PHONES WERE ON; THEY RESPONDED IN THE NEGATIVE. HOWEVER; THE FLT ATTENDANT SAID AT THE TIME THAT SHE HAD OBSERVED A PAX SEATED IN THE AFT OF THE ACFT TEXT-MESSAGING ON A CELL PHONE EARLIER DURING TAXI; AND THOUGH SHE SUBSEQUENTLY DIRECTED THE PAX TO TURN OFF ALL ELECTRONIC DEVICES; SHE LATER EXPRESSED REASONABLE SUSPICION THAT THIS INDIVIDUAL MIGHT NOT HAVE COMPLIED WITH HER INSTRUCTIONS. I MADE TELEPHONE CONTACT WITH DISPATCH AND MAINT. I COMMUNICATED OUR ENTIRE SITUATION TO THE MECH ON DUTY. I ALSO EXPLAINED OUR SUSPICION ABOUT THE CELL PHONE. HE AGREED WITH THAT POSSIBILITY OF CELL PHONE INTERFERENCE AND RESPONDED BY SAYING THAT WE SHOULD PERFORM THE BAGGAGE SMOKE WARNING SYS TEST; AND THAT IF THE SYS TEST WAS SUCCESSFUL THAT WE WOULD BE CLR TO CONTINUE THE FLT. I PERFORMED THE TEST AS DIRECTED IN THE FIRST FLT/POST MAINT CHKLIST; AND THE SYS TESTED NORMALLY. I THEN COMMUNICATED THAT INFO TO DISPATCH. OUR COLLECTIVE DECISION; BASED ON COM WITH MAINT; WAS THAT THE SYS WAS FUNCTIONING NORMALLY AND NO MAINT WRITE-UP WAS REQUIRED. DISPATCH THEN RELEASED US TO CONTINUE THE FLT. UPON REBOARDING THE PAX; WE THOROUGHLY EXPLAINED THE SITUATION TO THEM; AND REQUESTED THAT THEY PLEASE ENSURE ALL CELL PHONES REMAINED OFF FOR THE DURATION OF THE FLT. WE SUBSEQUENTLY CONTINUED TO ZZZ1 WITHOUT FURTHER INCIDENT.

Data retrieved from NASA's ASRS site as of May 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.