FLAGSTAFF, Ariz. (AP) An investigation into an Arizona wildfire that destroyed more than 30 homes and other buildings on the outskirts of Flagstaff last year concluded without investigators determining a definitive cause of the blaze, the U.S. Forest Service announced Friday.

Known as the Tunnel Fire, it was one of two major wildfires in the spring of 2022 on the outskirts of Flagstaff. The fire broke out Easter Sunday and grew to more than 29 square miles (76 square kilometers) due to a combination of strong winds and warm, dry conditions. Residents were forced to evacuate quickly, and firefighters spent weeks trying to extinguish the blaze before it was fully contained June 1.

The Forest Service’s investigative division in the Southwest said in a statement Friday that it had ruled out multiple potential causes during its probe but ultimately closed out the case without determining exactly what started the blaze. The agency did not immediately release its investigative report.

The fire started about 9 miles (14.5 kilometers) northeast of Flagstaff in an area of the Coconino National Forest where campfires are banned year-round. One of the intersecting forest roads near the fire’s origin, Schultz Pass, is a major artery for traveling around the San Francisco Peaks.

Residents at the time questioned how a small blaze was able to balloon into such a size, ripping through dry grass and scattered Ponderosa pines around homes into volcanic cinder fields. The flames threatened more than 1,330 structures and destroyed 30 homes and 24 buildings. No deaths were reported.

Matt McGrath, a district ranger on the forest, has said firefighters believed they had extinguished the fire when it was first reported and didn’t see any active smoke or flames when they checked on it the following day.

Winds were a major factor in the fire’s spread with flames soaring as high as 100 feet (30 meters). Popular national monuments, including Sunset Crater Volcano and Wupatki closed for a time because of the wildfire.

The other wildfire that followed on its heels, known as the Pipeline Fire, was still under investigation, said Brady Smith, a spokesperson for the Coconino National Forest.