ANCHORAGE — An environmental group filed a lawsuit Monday against the Federal Railroad Administration for failing to disclose the approval process for the Alaska Railroad’s application for rail shipments of highly volatile liquefied natural gas.

The Alaska Railroad would make the nation’s first rail shipments of LNG.

The Center for Biological Diversity filed the lawsuit in U.S. District Court in Washington, D.C., on Monday. Miyoko Sakashita, a senior attorney for the organization, said the federal agency has largely ignored a February public records request seeking information about the hazards of carrying LNG, other than acknowledging the request.

“We thought the urgent action was needed,” she said of the lawsuit.

“We’re really concerned that there hasn’t been an adequate safety and environmental review,” Sakashita told The Associated Press, adding that the lack of transparency “does not make me confident in their safety and environmental protections.”

Federal Railroad Administration spokeswoman Tiffany Lindemann said the agency does not comment on pending or potential litigation.

The railroad is not named in the lawsuit, and railroad spokesman Tim Sullivan said a reporter’s query was the first he had heard about it.

The federal agency in October 2015 issued a two-year permit to the railroad authorizing three round-trip trains between Anchorage and Fairbanks per week. The railroad, starting in late September, sent 40-foot LNG containers between the two cities as a demonstration. Altogether, two round trips a week were conducted for four weeks for the demonstration runs, according to Sullivan.

He said goal was to take information about efficiencies and logistics from the350-mile demonstration runs between Anchorage and Fairbanks before making decisions about their feasibility as a business.

“We haven’t come to any conclusions about it yet, but we’re still working out all the details,” Sullivan said.

Expansion of natural gas use is a longtime hope of Fairbanks residents looking for cheaper alternative to fuel oil for heating homes.

Natural gas also is part of a state plan to reduce some of the nation’s worst winter air pollution. The Fairbanks region regularly exceeds allowable federal levels for fine particulates, which can cause serious health problems.