AN INVESTIGATION is being conducted to determine how a piece of luggage caught fire on a conveyer belt at Suvarnabhumi Airport yesterday. The fire occurred at 6.35am when a Thai passenger was checking in for Bangkok Airway'Flight PG931 to phnom Penh, an airline statement said. The incident was resolved and is being handled by Airport of Thailand(AOT) . Raweewan nettarakavessana, director of Suvarnabhumi Airport, said an initial investigation showed that the luggage carried a leavening agent for fertiliser, which is believed to have undergone a chemical reaction, resulting in flames.