Federal regulators proposed civil penalties against three oil companies for allegedly failing to test North Dakota crude properly, which could have led to putting volatile oil into railroad tank cars too weak to handle it. The fines, while small, are the first penalties to emerge from a widening investigation into how the oil industry is testing the flammability of crude pumped from the Bakken Shale of North Dakota, and whether it is using tank cars strong enough to keep oil cargoes from exploding in case of a derailment. On Tuesday, the government proposed fines totaling $93,000 against Hess Corp. , Whiting Petroleum Corp. and Marathon Oil Corp. The companies allegedly either didn’t test—or improperly tested—crude oil bound for railcars. As a result, a combustible type of oil could have been loaded into railcars not designed to handle such volatile liquids, regulators said. Hess couldn’t be reached immediately for comment. […]