Fire rages near Yarnell, Ariz.

A team of expert firefighters were overrun by a massive wildfire near Yarnell, Ariz., while trying to make it to a safe zone after an unpredictable desert thunderstorm turned the fire into their path earlier this year, while confusing radio communications prevented a fire-fighting aircraft from dropping retardant on the blaze, according to a report issued Saturday.

The 119-page report, issued by the Arizona State Forestry Division on Saturday, cited failures in communication that prevented the team from keeping in touch with other crews battling the fire. Some radios were programmed to incorrect frequencies, the report concluded, meaning the team was out of contact for almost half an hour before the fire suddenly changed direction. But the report found no indication of recklessness or negligence on the part of the firefighters themselves.

It said the 19 members of the Granite Mountain Hotshots were moving from a mountain ridge toward a safety zone at Boulder Springs Ranch when winds from a passing thunderstorm caused the fire to overtake the team on June 30. The firefighters had less than two minutes to deploy emergency shelters; temperatures exceeded 2,000 degrees when the men were overtaken about 600 yards from the safety zone.

The Granite Mountain Hotshots, one of about 110 elite firefighting units in the United States, was attached to the Prescott Municipal Fire Department. Nineteen of their twenty members, ranging in age from 21 to 43, died in the blaze. Only one team member, who had been deployed elsewhere as a lookout, survived.

The Yarnell Hill fire was the deadliest single incident for firefighters since the Sept. 11, 2001, terrorist attacks killed 340 New York City firefighters, and the worst loss of life for firefighters in the western United States since 19 firefighters were killed in a refinery fire in Sunray, Tex., in 1956.

But the report drew no conclusions about why the firefighters left an earlier position atop a ridge, where they were relatively safe, in order to drop into the bowl and head toward the ranch.

“Our mission was to find out what happened and to discern the facts surrounding this tragedy to the best of our ability,” Jim Karels, a member of the review team and an official with the Florida Forest Service, said at a Saturday news conference in Prescott, according to the Arizona Republic.

The team that analyzed the sequence of events, which included local and state fire officials from all over the country, concluded that Arizona should review communications plans in wildfire situations, and that the state should review its coordination with weather forecasters.

The area hadn’t experienced a wildfire in more than 45 years, meaning the fire had plenty of fuel to speed its growth. Extreme fire danger, thanks to a summer-long drought, turned the trees to matchsticks.

The fire broke out around 5:30 p.m. on June 28, ignited by a passing lightening storm in a boulder field inaccessible by vehicle. At one point on that first day, the fire was less than half an acre in size and more than 80 percent burned out. Fire officials estimated it had little chance of spreading and putting surrounding towns at risk. Two small firefighting aircraft dropped fire retardant on the blaze early the following morning.

But by the afternoon of June 29, increasing winds helped the fire grow. By late afternoon, the fire had grown to about six acres and jumped a two-lane track road. The incident commander requested several more passes by firefighting aircraft, but high winds and severe weather prevented those larger-capacity aircraft from taking off. By evening, the fire had grown to about 100 acres, moving at a rate of up to 660 feet per hour toward Yarnell.

Early June 30, officials ordered the evacuation of residents of two subdivisions near Yarnell. The Granite Mountain Hotshots parked their crew carriers on Sesame Street, in Yarnell, and began hiking into the mountains. A recreational hiker snapped a photograph of the men, in full firefighting gear on a day when the temperature would reach 104 degrees, trudging upwards. A second hotshots team, operating a bulldozer nearby, spotted the Granite Mountain team working on the east side of a ridge, burning a two-track road in hopes of slowing the fire’s advance.

Around noon, the second team and the captain of the Granite Mountain team sent a scout from the Granite Mountain team, 21-year old Brendan McDonough, to the bottom of a slope that would provide a good vantage point. The captains of the two teams also discussed problems they were having with their radios. The Granite Mountain team worked behind the fire in an effort to ensure it wouldn’t double back on itself; they didn’t anticipate additional resources, given that most other crews and aircraft had been deployed to stop the fire’s advance to the north.

At 2 p.m., the National Weather Service office in Flagstaff warned fire officials that thunderstorms that would produce wind gusts of 35 to 45 miles per hour were developing east of the fire. By 3:50 p.m., aircraft supervisors warned the incident commander that the fire was just an hour or two from reaching Yarnell, and the Granite Mountain team’s vehicles. But the aircraft itself had to leave the area, given how long the pilot had been flying that day. Wind caused by a downdraft from the thunderstorm had picked up, fanning the flames and forcing McDonough to move.

Fifteen minutes later, Granite Mountain Hotshot Wade Parker, 22, texted a photo of the fire to a relative: “This thing is runnin straight for yarnel jus starting evac. You can see the fire on the left town on the right.” The wind had picked up so much that several other crews on other sides of the fire evacuated. The fire advanced a mile in just 15 minutes.

Weather also hampered efforts to combat the blaze by air. At some points during the day, firefighting aircraft weren’t available because of high winds. But at the time the Hotshots team deployed their emergency shelters, a large firefighting aircraft was stationed over the fire, trying to assess the crew’s location.

It is not clear when the team decided to move toward the ranch, which they had established as a backup safe zone. Within minutes of Parker’s text, radio communications from the Granite Mountain Hotshots became increasingly urgent. At one point, a senior member of the team radioed that they were about to be overrun. “[O]ur escape route has been cut off. We are preparing a deployment site and we are burning out around ourselves in the brush and I’ll give you a call when we are under the sh-, the shelters.”

An hour later, an Arizona Department of Public Safety helicopter, frantically searching for the team, spotted the emergency shelters. The pilot landed about 500 yards away; a paramedic hiked to the scene and found all 19 hotshots dead.

The Boulder Springs Ranch, its owners and the livestock that lived on the property were unharmed.