Arizona’s senators are demanding answers from the Department of the Interior over its handling of a devastating wildfire that is still burning out of control on the Grand Canyon’s North Rim.

In a letter sent Monday to Interior Secretary Doug Burgum, Democratic Sens. Ruben Gallego and Mark Kelly questioned the department’s initial response to the Dragon Bravo Fire. The blaze spread quickly over the weekend and destroyed dozens of structures, including the historic Grand Canyon Lodge, a visitor center and a wastewater treatment plant.

“It has been reported that National Parks Service officials initially decided to monitor the fire as a controlled burn, but changed their approach as strong winds allowed the fire to jump multiple containment features,” the senators wrote in the letter. “There are many questions over the initial decision to treat this fire as a controlled burn and subsequent decisions on how to respond.”

Neither the National Park Service nor the Department of the Interior immediately responded to requests for comment.

Arizona Gov. Katie Hobbs, a Democrat, on Sunday called for an independent investigation into the federal response, particularly the decision to “manage that fire as a controlled burn during the driest, hottest part of the Arizona summer,” she said in a post on X.

“An incident of this magnitude demands intense oversight and scrutiny into the federal government’s emergency response,” Hobbs wrote. “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.”

As of Monday, the fire had consumed more than 5,700 acres and remained 0% contained, according to InciWeb, the U.S. Forest Service’s wildfire information site.

Gallego and Kelly said they were concerned that early decisions by the federal government “may have affected the spread of fire in northern Arizona,” particularly since the North Rim has been under weeks of extreme heat and experienced a dry winter.

The senators asked Burgum to detail the factors that contributed to the initial decision to treat the fire as a controlled burn.

Controlled burns are fires that are intentionally set or allowed to burn to reduce the amount of dry and flammable vegetation in an area. These kinds of burns are used to manage ecosystems that need periodic fires to stay healthy and also to lower the risk of bigger wildfires from breaking out.

Gallego and Kelly called the Grand Canyon “Arizona’s crown jewel” and asked about the resources available to fight the wildfire. They also questioned how the Interior Department plans to prevent other blazes from spreading. The senators requested responses by Aug. 10.

The Dragon Bravo Fire was started by lightning on July 4. The National Park Service said Sunday that the blaze “exhibited extreme and volatile fire behavior the evening of July 12, resulting in a 500-acre expansion.” The fire’s rapid expansion was fueled by sustained winds of 20 mph and gusts reaching up to 40 mph, according to the NPS.

Early assessments suggest that between 50 and 80 structures have been lost, but no injuries or deaths have been reported so far.

A separate, bigger blaze known as the White Sage Fire is also burning north of the Dragon Bravo Fire. The White Sage Fire has consumed more than 49,000 acres and is also 0% contained,