Edited sentence: Although strong in compression, cast iron was known to be brittle in tension or bending, yet on the day of the accident the bridge deck was covered with track ballast to prevent the oak beams supporting the track from catching fire.Each girder was strengthened by wrought iron bars along the length.However, on 24 May 1847, a local train to Ruabon fell through the bridge.It was built using cast iron girders, each of which was made of three very large castings dovetailed together.It was finished in September 1846, and opened for local traffic after approval by the first Railway Inspector, General Charles Pasley.Stephenson took this precaution because of a recent fire on the Great Western Railway at Uxbridge, London, where Isambard Kingdom Brunel's bridge caught fire and collapsed.The accident resulted in five deaths (three passengers, the train guard, and the locomotive fireman) and nine serious injuries.The bridge had been designed by Robert Stephenson, and he was accused of negligence by a local inquest.There are many examples of forensic methods used to investigate accidents and disasters, one of the earliest in the modern period being the fall of the Dee bridge at Chester, England.This act imposed a heavy extra load on the girders supporting the bridge, and probably exacerbated the accident