As lawsuits over the BP oil spill mount, a group of conservationists and fishermen have a new target: the U.S. Department of Interior’s Minerals Management Service.

Earthjustice, an environmental law firm, and New Orleans’ Waltzer & Wiygul filed suit in federal court on Tuesday against the federal agency. The suit — Gulf Restoration Network and Sierra Club v. Salazar — charges that the agency violated federal law by exempting oil companies that drill in the Gulf of Mexico from disclosing blowout and worst-case spill scenarios as well as plans for dealing with them before approving the companies’ offshore drilling plans.