text: Smoking on Underground trains was banned in July 1984, over three years before the fire. Following a fire at Oxford Circus station in November 1984, the ban was extended to all Underground stations in February 1985. However, smokers often ignored this and lit cigarettes on the escalators on their way out. The inquiry found that the fire was most probably caused by a traveller discarding a burning match that fell down the side of the moving staircase on to the running track of the escalator. The police decided that the fire had not been started deliberately, as there was no evidence that an accelerant had been used and access to the site of the fire was difficult. Investigators found charred wood in eight places on a section of skirting on an escalator and matches in the running track, showing that similar fires had started before but had burnt themselves out without spreading. The investigators found a build-up of lubricant grease under the tracks, which was believed to be difficult to ignite and slow to burn once it started, but it was noted that the grease was heavily saturated with fibrous materials (fluff from clothes, tickets and other small litter, human hair, rat fur, etc.). A test was conducted where lit matches were dropped on the escalator to see if ignition would occur. Dropped matches ignited the contaminated grease and the fire began spreading. It was allowed to burn for nine minutes before being extinguished.