The visitor center and a wastewater treatment plant were among the 50 to 80 structures lost, the park superintendent said. The area was evacuated Thursday.

Parts of Grand Canyon National Park remained closed to the public Sunday because of wildfires and the release of chlorine gas from a North Rim water-treatment facility, the National Park Service said.

The inner canyon, including Phantom Ranch, was closed, as were trails to the inner canyon, because a water treatment facility on the North Rim was damaged by fire and was leaking chlorine gas, park officials said. Chlorine gas is toxic and is heavier than air, meaning it could settle into the lower part of the canyon.