An A319's number two engine fire warning alerted as the engine was being started and both bottles were fired; but another airline crew and Airport Rescue and Fire Fighting saw no signs of a fire. The aircraft was returned to the gate.

Narrative

During taxi-out abeam the fire station; the First Officer began number 2 engine start. Almost immediately fire warning bell and ECAM engine 2 fire warning were annunciated. I stopped the aircraft; set the parking brake; and called for ECAM actions. The First Officer performed ECAM actions. I stated 'Flight Attendants stations' on the PA and advised Ground Control we were declaring an emergency for engine 2 fire warning and to scramble the fire trucks. The fire warning ceased after the First Officer fired the first fire bottle but came back almost immediately. He fired the second fire bottle and the fire warning ceased. Another aircraft behind us heard our condition and stated there was no fire or smoke present from our number 2 engine. The fire trucks arrived and stated on Ground Control frequency there was no fire or smoke indications and thermal imaging also revealed no hot spots. I told the Lead Flight Attendant what we had and to advise if he saw anything abnormal. He did not. With concurrence of the fire chief we taxied back to the gate with fire trucks monitoring. I told the passengers we had experienced an engine malfunction and were returning to the gate. On arrival at the gate we shut down and deplaned the aircraft normally.