Airport Explosion

yesterday when i was entering the new airport for a flight back to the states i heard a very loud explosion come from the somewhere outside. maybe in the lower levels. it was very shocking to say the least. everyone kind of looked around and at each other but no one could tell where it came from or what it was. security at the door just looked around but didnt get on the radio or rush to find out. and i didnt want to stand around there and went inside where i thought it would be safer. it was a really huge explosion. anyhow when i checked in i asked at the counter about it. they made a call and said they had no info on it. so i continued and got on my flight which was delayed for an hour. not sure why. anyhow it really freaked me out and i see no information on it online bkk news. does anyone else know anything. the only thing i can think if it wasnt a bomb maybe it was a propane tank on a taxi or something. it was too big to have not hurt someone near by. at least hurt there ears. anyhow im really curious as to what it was. anyone know?