(Reuters) - An elite squad of 19 Arizona firefighters killed in the worst U.S. wildland fire tragedy in 80 years apparently was outflanked and engulfed by wind-whipped flames in seconds, before some could scramble into cocoon-like personal shelters.

Details of Sunday's deaths of all but one member of the specially trained, 20-man Granite Mountain Hotshots were vague a day after they died in a blaze that destroyed scores of homes and forced the evacuation of two towns in central Arizona.

But fragments of the firefighters' final moments painted some of the picture as an investigation was launched into how the disaster unfolded and their remains were borne away in a cortege of 19 white coroner's vans to Phoenix for autopsies.

The solemn procession from the team's home base in the town of Prescott was welcomed by a police and firefighter honor guard after passing beneath a flag-draped arch of ladders extended from two fire trucks parked on either side of the roadway.

Fire officials said the fallen men, most in their 20s, were victims of a highly volatile mix of erratic, gale-force winds, low humidity, a sweltering heat wave and thick, drought-parched brush that had not burned in some 40 years.

The deaths brought an outpouring of tributes from political leaders, including U.S. President Barack Obama, who is on an official trip to Africa. Arizona Governor Jan Brewer called the deaths "one of our state's darkest, most devastating days" and ordered state flags flown at half staff through Wednesday.

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