Oil exports in the United States have hit a 15-year high, and most is getting shipped north of the border, to Canada, according to recent data from the U.S. Energy Information Administration.

U.S. transportation officials pressed for companies to come up with safer ways to transport oil the nation's rail lines following some explosive accidents.

Following a string of explosive accidents, federal officials say crude oil being shipped by rail from the Northern Plains across the U.S. and Canada may be more flammable than traditional forms of oil.