A flashlight battery overheated in luggage located in a B737-800's aft cargo compartment and caused the AFT CARGO FIRE warning to alert. The crew declared an emergency and diverted to a nearby airport where the hot luggage was found after an inspection.

Narrative

We were climbing through approximately 26;000 FT when we received a fire warning for the aft cargo compartment. We immediately declared an emergency and made a left turn with a rapid descent toward a nearby airport. We completed the Cargo Fire Checklist and the fire warning light went out. We called the Flight Attendants and asked them if they noticed anything unusual. They reported they did not. We the ran the emergency landing checklist and the before landing checklist. The Captain made a PA to the passengers and completed the TEST items to the Flight Attendants informing them we would be landing in ten minutes. The weather was VFR with light winds and we requested a straight in visual to the runway. Just before an overweight landing at 146;000 LBS the AFT CARGO FIRE warning light came back on. We came to stop on the runway and the Fire Chief came up on our radio frequency. We directed him to our aft cargo door to give us a temperature reading. He did not detect any heat so we made the decision not to evacuate. Mobile lounges were immediately brought up to the aircraft and all the passengers and Flight Attendants were quickly deplaned. All the luggage was removed from the aft cargo compartment and we were told two suspect bags had elevated temperatures. We were later informed a flashlight had started a fire in a suitcase. After all clear by the Fire Chief we were towed to a hardstand by Company personnel.