Before this weekend’s fiery Norfolk Southern train derailment prompted emergency evacuations in Ohio, the company helped kill a federal safety rule aimed at upgrading the rail industry’s Civil War–era braking systems, according to documents reviewed by the Lever.

Though the company’s 150-car train in Ohio reportedly burst into 100-foot flames upon derailing — and was transporting materials that triggered a fireball when they were released and incinerated — it was not being regulated as a “high-hazard flammable train,” federal officials told the Lever.

Documents show that when current transportation safety rules were first created, a federal agency sided with industry lobbyists and limited regulations governing the transport of hazardous compounds. The decision effectively exempted many trains hauling dangerous materials — including the one in Ohio — from the “high-hazard” classification and its more stringent safety requirements.