Hundreds of firefighters working from the air and ground in Arizona are battling the so-called Dragon Bravo blaze.

More than 500 tourists and park staffers have been evacuated since the fire broke out on July 4, apparently from a lightning strike.

On Saturday night the flames intensified quickly due to sustained winds gusting at up to 40 miles (64 kilometers) per hour, the National Park Service said.

According to early assessments, the fire has burned down between 50 and 80 structures, including administrative buildings, a water treatment facility, and a historic building called Grand Canyon Lodge.

It is the only place on the North Rim inside the park where visitors can spend the night. It was rebuilt in the 1930s after being destroyed in a fire and declared a national historic monument in 1987.

Burning for over a week, the fire was initially managed by federal authorities in a confine and contain strategy -- rather than being tackled aggressively to try to put it out.

Arizona Governor Katie Hobbs has criticized the approach and called for an independent probe.

"An incident of this magnitude demands intense oversight and scrutiny into the federal government's emergency response," she wrote on X.

"They must first take aggressive action to end the wildfire and prevent further damage. But Arizonans deserve answers for how this fire was allowed to decimate the Grand Canyon National Park," the Democratic governor wrote.

Authorities announced the North Rim is now closed for the remainder of the tourism season running through mid-October.

Firefighters are also battling a second blaze around 35 miles (56 kilometers) north of the Dragon Bravo fire in Kaibab National Forest.

Roads have been closed down too but the more popular South Rim of the canyon remains open.

Dozens of fires are burning in the western United States as the country goes into a dry and dangerous season for wildfires.

The region faces additional challenges because the Trump administration has cut funding and staff at federal agencies that work to prevent and grapple with fires and other natural disasters.

One of the greatest wonders of the natural world, the Grand Canyon is the result of the Colorado River eating away at layers of red sandstone and other rock for millions of years, leaving a chasm up to 18 miles wide and more than a mile deep.

Last year almost five million people visited the world-famous site.