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.

What fueled the explosive growth of the Dragon Bravo Fire was a mix of gusty winds, dry air and above-normal heat – weather conditions experts described as atypical for this time of year, when monsoonal moisture typically tamps down wildfire risk across Arizona.

A water treatment facility at the North Rim had been compromised by the fire, causing chlorine gas to fall towards the bottom of the canyon.