SEATTLE  A plan to build the United States’ first West Coast facility for exporting coal to Asia has come under increased scrutiny after the disclosure of documents suggesting that the company proposing the project did not convey the full scope of its plans to state regulators here in Washington.

The project, which would be built on the Columbia River in Longview, Wash., received preliminary approval from Cowlitz County commissioners late last year but has been delayed by a legal challenge by environmentalists.

They claim that supporters of the facility  which would transfer coal brought by train from Montana and elsewhere to barges bound for China and other parts of Asia  have not adequately measured the pollution that could be caused by shipping the coal and then burning it overseas.

The project has been has controversial because it pits the economic ambitions of Western states like Montana, which has vast coal reserves, and Washington, which depends heavily on trade with Asia, against the Northwest’s well-established environmental principles and clean energy goals. The Port of Vancouver in British Columbia already exports American coal, but political opposition has played a role in keeping coal out of United States ports so far. Another facility is being proposed near Bellingham, Wash.