Ventilation fans inside that tunnel to begin activating. Of course, it was rapidly filling with smoke. The ntsb says there was also severe arcing damage. And we also know that many of those passengers were on that train for about an hour. So it appears now from this report that the ntsb essentially knew what the trouble began but they dont know why. Theyre looking to a number of things. Was there damage somehow to that third rail . Was there a surge in electricity . Did something hit that rail . Right now, they dont know. Typically, the ntsb investigation can take quite a lodge time. They say theyre going through all the maintenance records and training records. Theyve been doing witness interviews but this investigation is expected to be comprehensive. It could take between six months and a year. Live in southwest washington richard reid abc 7 news. Thank you richard. Stay with abc 7 for the latest on the metro smoke investigation. 7 on your side team will keep digging for answers int