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 firefighting aircraft from dropping retardant on the blaze, according to a report issued Saturday.

The 119-page report from the Arizona State Forestry Division on 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. The surviving team member had been deployed elsewhere as a lookout.

The Yarnell Hill fire was the deadliest single incident for firefighters since the Sept. 11, 2001, terrorist attacks killed 343 members of the New York Fire Department, 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.

The Yarnell Hill Fire burns on June 30, 2013. (David Kadlubowski/AP)

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 the state’s 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 because of 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 lightning 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.