They're not exactly sure what they are looking for, but it must be here somewhere. Amid the charred pine needles and blackened forest debris is the cause of this still smoldering fire - if only they could find it.
What the students attending the federal wildfire investigation course don't yet realize is that one of them stepped on the evidence while trying to understand the burn patterns on nearby brush. Only a single staple from the blackened matchbook was left.
It was a beginner's mistake but also an indication of how fragile a fire investigation can be.
Every year, thousands of wildfires burn public lands, and as the drought in the West gives rise to more destructive fires, the demand for trained fire gumshoes and thorough investigations has only increased.
``We need to equip all our people, with all the resources they need so that every fire gets a good investigation,'' said Mike Heath, a senior instructor for the Federal Law Enforcement Training Center, which sponsored the five-day training in Prescott. ``When it gets busy, it's hard to give every fire the attention needed.''
The training center, a division of the Department of Homeland Security, trains about 250 to 300 fire investigators a year during eight to 10 training sessions around the country.
The agency has offered the training for years, but interest has picked up substantially in the last several years, Heath said. Terrorism fears have brought more students from agencies like the FBI, while large ravenous fires in the West have increased attention from public lands workers.
Some students who attend are seasoned investigators looking to brush up their skills, but others are rangers or firefighters who could be among the first to arrive at a fire.
Training them can help ensure that the site of the fire's start is preserved for later investigation, said Mike Reamer, a patrol captain for the Prescott and Kaibab national forests.
``A lot of the investigations fall back on the guys on the ground,'' he said.
Most times, the firefighters first responding to a wildfire are preoccupied with finding a safe place to battle the flames, said John ``Pancho'' Smith, a Forest Service agent who handles investigations on larger fires in Arizona.
``Usually what happens is the first fire engine on the scene will be parked on the point of origin,'' he said half-joking.
Finding the origin and source of a fire is a crucial step in determining who started the fire and whether it was intentional.
In destructive arson fires, the investigations can be used to prosecute perpetrators. The penalty for starting a fire can range from a $100 fine to the cost of fighting a wildfire, which can be in the millions of dollars. If there's criminal intent, a fire starter can get prison time.
Even in cases that are accidental, the investigation information can be used to refine education programs or develop other prevention efforts, said Reamer.
While finding the source of some fires can be more difficult than others, Heath said investigators like to believe there is always something left to indicate how a wildfire started, even amid thousands of acres of burnt land.
The evidence can be tiny round pellets smaller than BBs, from a catalytic converter, or blackened jagged metal fragments, the remnants of welding, or slender straight metal rods, left over from sparklers.
Instructors ``teach them to look for something that doesn't belong,'' said Heath.
That's part of the point of the class, which covers everything from burn patterns to witness interviews to report writing. ``They'll see that it can be done,'' Heath said.
Wildland fires burn in fairly predictable patterns. They generally move in a V-shape away from the source of the fire, helping investigators narrow the initial site. Often evidence of the fire's origin is left because wildland fires gain intensity as they move away from the source, meaning some of the least damaged areas can be near the start, said Reamer. House fires, in contrast, usually have the most intense damage near the start because of the confined space.
Still, looking for the cause of a wildfire requires patience. After investigators read the burn patterns to narrow the origin site, they'll carefully comb the 10-foot-by-10-foot or so area, sometimes using a magnifying glass and magnets.
``This takes a lot of practice. It's more of an art than a science,'' said Reamer.
Robin Thies, an investigation student from the Tonto National Forest, said the classroom information she and other students were given was clear and concise, but the burn investigation exercise gave them a good flavor for how difficult investigations can be.
``In the real world, it's not that clear,'' she said. v Smith, who was attending the class as refresher but has investigated fires for years, said real-world fires add a host of complications from swirling winds to slurry drops to Hotshot crews crisscrossing the evidence scene.
Even after the source of the fire is determined, investigators must interview people who were hiking or camping in the area, track down those who were in a particular parking lot or do other police work.
``In the process of all that, there's another fire and another fire and another fire,'' Smith said.