A spokeswoman for Maryland's attorney general said the state is suing the U.S. Environmental Protection Agency for failing to act on a petition requiring power plants in five upwind states to reduce pollution.
Raquel Coombs, a spokeswoman for Attorney General Brian Frosh, told The Associated Press the lawsuit will be filed Wednesday after weeks of preparation.
Gov. Larry Hogan directed the attorney general to sue the EPA Wednesday morning. The Hogan administration says 70 percent of Maryland's ozone problem originates in upwind states.
Maryland petitioned the EPA in November for a finding that 36 power plant units in Indiana, Kentucky, Ohio, Pennsylvania and West Virginia are emitting air pollution affecting Maryland.
In January, the EPA issued a six-month extension to act, setting a July 15 deadline that expired without action.