Up to 30 carriages have fallen on to a highway in Georgia after a train derailed on a bridge, according to US authorities.The entire population of Byromville - about 500 people - was evacuated following the accident, which happened at around 7am local time.Fire chief Brett Wallis told WMAZ-TV that between 15 and 30 carriages had fallen on to Georgia Highway 90, with some of them said to contain propane gas.Operator CSX Railroad has confirmed that the train had 72 loaded carriages and 69 empty ones.No injuries have been reported but several roads have been closed in the area, with traffic being diverted as police assess the damage.