JACKSON, Miss. (AP) — The head of the Mississippi Development Authority has rejected an appeal by opponents who sought to block rules for offshore gas and oil exploration and leasing.

In a Friday letter to Sierra Club attorney Robert Wiygul, MDA Director Brent Christensen writes that the rules were properly adopted. Opponents had expected the ruling after a hearing officer earlier recommended to Christensen that he not overturn the rules.

The Sierra Club and the Gulf Restoration Network, who are fighting plans by the state to lease parts of the Mississippi Sound for natural gas drilling, repeat that they plan to appeal to Hinds County Chancery Court.

The environmental groups say the state failed to consider the impacts of actual drilling, instead only considering the impacts of leasing, when leasing will lead to drilling.