The National Wildlife Federation filed a lawsuit this week charging the U.S. State Department is refusing to disclose public information about a pipeline company’s possible plans to transport dangerous tar sands oil from Montreal to the coast of Maine.

The lawsuit takes aim at the oil industry’s repeated claims that there is no plan to transport the dirty oil through New England, despite numerous indications that such a plan indeed exists.

A 70-year-old, 236-mile pipeline, owned by Portland Pipeline Corporation (which is majority owned by Exxon-Mobile), currently transports crude oil from freighters in the city of South Portland, Maine to Montreal.

Yet, environmental and community organizations say there are strong signs that PPL and parent company Montreal Pipe Line Company is planning to reverse the flow of the pipeline in order to transport tar sands oil from Canada to South Portland where it would then be distributed to international markets via oil tankers and an upgraded terminal.

NWF is accusing the State Department of refusing to respond satisfactorily to a Freedom of Information Act request (pdf) filed over two years ago for public documents about such plans.