THE MAIN ANNUNCIATOR ENG FIRE LIGHT ON A BA31 ILLUMINATED AFTER THE ACFT WAS TAXIED ONTO THE RWY. THE FLC DECLARED AN EMER; AND FOLLOWED ALL PROCS BEFORE FIRE TRUCKS ARRIVED. PAX WERE EVACED.

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HAD FIRE INDICATION ON R ENG. FOLLOWED MEMORY ITEMS AND CHKLIST FOR ENG FIRE CAP LIGHT. EVACED PAX. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR (CAPT) AND FO HAD JUST BEEN RAMP CHKED. IT WAS SNOWING; AND THE VISIBILITY VARIED BTWN .5 TO 1 MI. THE ACFT WAS DEICED; BUT BECAUSE OF ALL OF THE ACFT ON HOLDOVER TIMES; THE FLC HAD TO RETURN TO THE GATE FOR A SECOND DEICING. AFTER THE SECOND DEICING; THE FLC TAXIED OUT AND WAS CLRED ONTO THE RWY FOR TKOF; SHORTLY AFTERWARDS. WHEN THE ACFT WAS TAXIED ONTO THE RWY; THE ENG FIRE CAP LIGHT ILLUMINTED. THE FLC DECLARED AN EMER; AND FOLLOWED CHKLIST PROCS -- FIRING BOTH BOTTLES. MAINT TOLD THE RPTR THAT THEY FOUND NO EVIDENCE OF FIRE AND THAT THE FALSE WARNING WAS A RESULT OF A BAD FIRE WIRE; BUT THE CAPT SAYS THAT THE SAME THING HAPPENED TO ANOTHER FLC A WK LATER (SAME ACFT AND SAME ENG); WHILE THEY WERE ON FINAL APCH. THE CAPT THINKS THAT THE PROB WAS RELATED TO A BLEED LEAK. THE HEAT FROM A BLEED LEAK COULD BREAK DOWN THE RESISTANCE IN THE WIRE AND ACTIVATE THE WARNING. THE RPTR BELIEVES THAT THIS IS TRUE BECAUSE THE ANNUNCIATOR EXTINGUISHED ABOUT 10 MINS AFTER THE BOTTLES HAD BEEN FIRED. A BAD FIRE WIRE WOULD HAVE CAUSED THE ANNUNCIATOR TO REMAIN PERMANENTLY ILLUMINATED.