An unidentified substance has killed or injured hundreds of birds so far.
Crude-by-rail has been a growing concern as an oil boom in North Dakota has meant more and more crude is traveling to refineries by rail. A series of fiery derailments in the past year has focused attention on the need for accident prevention and emergency response preparation.
Beginning Saturday, railroads must notify states when large shipments of crude oil come through by train. The new rule is in response to safety concerns with crude-by-rail.