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

The Dragon Bravo Fire has destroyed dozens of structures and a water treatment facility, and the White Sage Fire, located in Kaibab National Forest, has forced hundreds to evacuate.