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 Grand Canyon Lodge opened in 1937 and was the only hotel located inside Grand Canyon National Park on the North Rim.