On 26 August 2020 a freight train carrying diesel fuel and gas oil in tank wagons derailed at Morlais Junction, Llangennech, Carmarthenshire, Wales. Some of the derailed wagons caught fire, leading to an evacuation of people living nearby. There was widespread contamination from the spilled fuel. The clean-up operation was described by Natural Resources Wales as the most challenging since the Sea Empress oil spill in 1996. The accident was caused by defective brakes on a wagon causing an axle to seize, which in turn caused deformation of the track under the train as it travelled over a set of points. The Heart of Wales Line was closed for seven months as a result of the derailment.