RALEIGH, N.C. — The country’s largest electric company is refusing online access to federally mandated maps showing the scope of disaster resulting if a coal-ash pit burst and spilled its toxic muck onto neighboring properties.

Advocacy groups Southern Environmental Law Center and Earthjustice said Wednesday they’re planning to sue Duke Energy Corp. Environmentalists say the information is blacked out for more than a dozen Duke Energy sites in Indiana, Kentucky and North Carolina.

The groups say the Charlotte-based company is the country’s only electric utility not providing the Dam Safety information online.

The Associated Press found the Tennessee Valley Authority, Alabama Power and Ohio-based American Electric Power among those posting the maps required by a two-year-old Environmental Protection Agency rule.

Duke Energy spokeswoman Erin Culbert said local emergency workers are given all details.