An investigative report into the deaths of 19 firefighters killed in June while battling a blaze in Arizona has found that problems with radio communication played a key role in the tragedy.

In a cruel twist, the report says at the moment the firefighters were killed, an air tanker carrying fire retardant was hovering overhead, waiting for an update about their location.

All but one member of the Granite Mountain Hotshots crew died June 30 while protecting the small former gold rush town of Yarnell, about 80 miles northwest of Phoenix, from an erratic lightning-sparked wildfire.

The fire ended up destroying more than 100 homes and burned 13 square miles before it was fully contained on July 10.

No other wildfire had claimed the lives of more firefighters in 80 years, and it was the deadliest single day for fire crews since the terror attacks of Sept. 11, 2001. The Granite Mountain team was unique among the nation's roughly 110 Hotshot crews as the first and only such unit attached to a municipal fire department.

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The Arizona State Forestry Division presented the roughly 120-page report to the men's families ahead of a news conference Saturday morning in Prescott.

The report states that on the afternoon of June 30, the 19 members of the Granite Mountain Hotshots crew were on a ridge while the fire moved away from them. However, at around 4 p.m., the crew left the ridge and went to a ranch dubbed the "safe spot." It is still not clear why the men left their position on the ridge, and the answer may never be known.

Investigators said Saturday that no one asked the firefighters to change location, and for 30 critical moments, there was no radio contact that could have determined their location.

"As far as we know, their radios were working. They could communicate, they just did not communicate, some of that is pretty common," Scott Hunt of the Arizona State Forestry Division told MyFoxPhoenix.com.

Sometime after the firefighters reached their new location, the fire changed direction, overrunning the crew, while reaching temperatures of 2,000 degrees Fahrenheit, similar to lava.

The report says they had two minutes to clear a safe spot and deploy shelters.

"Whatever you had would not have been survivable," said Mike Dudley, a member of the State Forestry Division investigative team.

In the last radio communication from the firefighters, the division leader says,"Granite Mountain Hotshots Division Alpha. We are burning out around ourselves in the brush and I'll give you a call when we are under the shelters."

At one point, officials asked for half of the available western U.S. heavy air tanker fleet -- six planes -- to try to control the blaze. Five weren't deployed because of the limited number in the nation's aerial firefighting fleet and the dangerous weather conditions at the time. One plane was heading to Arizona from California but engine problems forced it to turn back.

Some family members hope the investigation will bring closure. Others say it will do nothing to ease their pain.

"No matter what the report says, it won't bring him back," Colleen Turbyfill said of her son, Travis. "I miss him, and it's unbearable pain. It doesn't go away. Sometimes I can't breathe, but this report isn't going to help that one way or another."

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The Associated Press contributed to this report.