How wildfires spread
Firefighters have managed to contain 45% of a blaze in central Arizona that killed 19 of their colleagues, the authorities say.
Some 114 buildings have been damaged or razed by the fire, which has burned 13 sq miles (33 sq km).
Officials say they cannot rule out the possibility some residents who refused to evacuate also perished in the blaze.
The deadliest US wildfire in 80 years, it was ignited by lightning in forest around the town of Yarnell.
On Wednesday, nearly 600 firefighters were fighting the blaze, which has been fuelled by 40mph winds and dry conditions.
The Southwest Incident Command Team tweeted that nearly half of the fire was contained.
Arizona Governor Jan Brewer has ordered state flags to be flown at half-mast for 19 days to honour each firefighter lost.
Only one member of the unit survived, a lookout on higher ground who was about a mile away from the others.
Hundreds of residents were evacuated, but some refused to leave. Authorities fear finding more bodies during the clearing-up operation.
"This fire moved approximately four miles in 20 minutes," Yavapai County Sheriff Chief Deputy John Russell told Reuters news agency.
"We had already started evacuating everyone... and we experienced people who were not going to leave."
Fire investigators are trying to determine how the members of the elite Granite Mountain Hotshots became trapped by the flames.
The inquiry team, which includes forest managers and safety experts, is expected to release a preliminary report within days.
Sunday's tragedy marked the greatest loss of life from a US wildland blaze since at least 25 men died in 1933 battling the Griffith Park fire in Los Angeles.
A fire needs fuel, oxygen and heat to burn. The fire threatening the town of Yarnell was started by lightning and spread rapidly in the very hot, dry conditions, fanned by strong winds
The fastest-moving and most dangerous part of the fire is known as the "head". Areas ahead of the fire are warmed as it approaches and flying embers blown by the wind spark spot fires, which cause it to leap further ahead
Some vegetation or fuel will burn quicker than others and this creates "fingers" of flame which, in turn, create pockets of land surrounded by fire, making it harder to tackle
Fires travel faster uphill than downhill, as the heat and smoke rise, heating areas higher up the hill and wind currents also tend to blow uphill, pushing the flames further. Burning embers may roll downhill, starting new fires