An investigation into the June deaths of 19 firefighters killed while battling an Arizona blaze has found a litany of problems stemming from inadequate radio communication.

The report by a team of fire experts cited improperly programmed radios, vague updates and a 3-minute communication blackout just before the flames engulfed the men. It was released Saturday.

It also said there was 33-minute "gap in the information available for the Granite Mountain IHC (Interagency Hotshot Crew)."

"From 1604 to 1637 (4:04 p.m. to 4:37 p.m. on June 30), the team cannot verify communications from the crew, and we have almost no direct information for them," the report's executive summary said. "There is much that cannot be known about the crew's decisions and actions prior to their entrapment and fire shelter deployment around 1642 (4:42 p.m.)"

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.

The 20-member Granite Mountain Hotshots team arrived on June 30 to fight the fire outside Yarnell, about 80 miles northwest of Phoenix. About nine hours later, the crew radioed that they were trapped by flames and deploying their shelters. One crew member who was assigned as the lookout survived.

The fire had taken a sudden turn as the result of thunderstorm winds, and its speed and intensity cut off the path to a designated safety zone for the firefighters, the report said.

The report and a briefing on it were released privately to surviving family members of the firefighters before it was publicly released Saturday morning.

Read the report here, courtesy of the Arizona Republic