Hot spots remained in the White Tail Canyon area as the Horse Shoe 2 destroyed two of about 20 structures in the area last night. David Sanders/Arizona Daily Star

The two largest wildfires burning in Southern Arizona originated in rugged, mountainous corridors frequently used by cross-border people and drug smugglers.

And the U.S. Forest Service has determined that both fires were human-caused.

So even though the investigations remain open, speculation is ablaze that illegal immigrants or smugglers are responsible for the Horseshoe 2 Fire northeast of Douglas and the Murphy Complex Fire northwest of Nogales.

"It's definitely not caused by somebody on a picnic whose wiener overcooked," resident Brad Titcomb said about the Murphy Fire, which came within a mile of his house in the Aliso Springs neighborhood west of Tubac. "This is illegal traffic one way or another."

At a press conference last week, Coronado National Forest supervisor Jim Upchurch said causes of fires include ricocheting bullets, campfires, welding equipment and possibly ignition by smugglers or illegal immigrants. But when asked specifically about the Horseshoe 2 and Murphy Complex fires, Forest Service officials say only that they are human-caused and under investigation.

The Horseshoe 2 Fire has burned 128,652 acres in the Chiricahua Mountains - including three homes and six buildings. The Murphy Complex Fire has burned 68,033 acres in the Tumacácori and Atascosa mountains - including the historic Atascosa Lookout.

Both rank among the top 10 largest wildfires in Arizona since 1990, shows information from the Southwest Coordination Center, which manages firefighting activities in the Southwest.

Don't expect definitive answers on who set the blazes - many human-caused fire cases are never solved.

Finding the culprit is daunting for fire investigators, said Pat Schneider, an assistant U.S. attorney in Arizona for the past 20 years who has experience on cases stemming from wildfires including the well-known Rodeo-Chediski Fire of 2002.

More than 70 percent of Arizona is federal land and the number of law enforcement officers is limited, he said. And wildfires believed to be caused by people are frequent - 142 fires of more than 100 acres in Arizona from 2003 to 2010, show data from the Southwest Coordination Center.

"Many times, the cases we are able to make and prosecute are when the suspect is caught in the act or soon thereafter, or because someone from the public helps as our eyes and ears," Schneider said. "The problem with fire, depending on how it burns, is that many times fire destroys a lot of evidence that was there."

The U.S. Attorney's Office in Arizona has handled just a few wildfire cases each of the past two years, he said. He didn't recall any prosecution of illegal immigrants in connection with wildfires.

Pinpointing a cause

Annual fire reports from government agencies focus solely on how many fires were caused by people versus lightning, said Carrie Templin, spokeswoman with the Bureau of Land Management.

The Horseshoe Fire, which started on May 31, 2010, and burned 3,400 acres in the Chiricahua Mountains northeast of Douglas, remains under investigation, said Coronado Forest spokeswoman Heidi Schewel.

Like the Horseshoe 2 Fire, there was no lightning in the area, so both are classified as human-caused.

With fires presumed to be started by people, the focus is on finding a specific cause - not on determining where the people were from, said Mary Zabinski, fire information officer at the Southwest Coordination Center.

Cause of fires in Southeastern Arizona include sparks from electrical equipment and tailpipes, matches and cigarettes and sometimes strange occurrences, such as a bear getting electrocuted on a power pole and falling to the ground on fire, Zabinski said.

But the most common cause of fires, in Arizona and nationwide, is abandoned campfires, Zabinski said. Officials often see a rash of them on holiday weekends.

The Murphy Complex Fire was started on May 30 - Memorial Day. That was not lost on Jim Cumming, who lives in a house west of Rio Rico built by his family in 1946.

"If you are betting odds, it was probably caused by illegal immigrants," Cumming said about the Murphy Complex Fire. "But being that it was caused on Memorial Day, it could have been caused by a camper. It's anybody's guess who started it."

Hot spot for crossers

The Murphy Complex Fire is burning west of Nogales, stretching from south of the international border to about 18 miles northwest of Tubac. It is the combination of two blazes that met up: the Pajarita and Murphy fires.

The flames are raging right in the heart of a smuggling corridor commonly used by drug runners and rip crews.

Border Patrol agent Brian Terry was fatally shot in the same area during a shootout between agents and suspected border bandits on Dec. 14, 2010. The corridor has been a hot spot for confrontations between smugglers and criminals dating back to 2007.

Hikers, hunters and outdoor enthusiasts sometime go up there, but the area is primarily used by drug smugglers and illegal immigrants, said Lt. Raoul Rodriguez of the Santa Cruz County Sheriff's Office. That's why he believes it's fair to speculate they started this most recent fire.

Cumming doesn't believe the fire was started intentionally, whether by illegal immigrants or U.S. citizens.

"It was definitely human-caused," Cumming said, "but by human error."

Smugglers don't generally set fires purposely as diversions, said Border Patrol Tucson Sector spokesman Mario Escalante.

But they regularly make fires to cook, or to keep warm during the colder months, said Brandon Judd, president of Local 2544 of the National Border Patrol Council, the union representing agents in Arizona. In the areas where the Murphy Complex Fire and Horseshoe 2 Fire started, the only people agents encounter are illegal immigrants or drug smugglers, he said.

"We definitely believe that the majority of these fires are started by illegal aliens," Judd said.

At the height of the Murphy Complex Fire, firefighters laid a fire retardant 100 yards from area resident Titcomb's ranch-style house he's owned for 15 years in Aliso Springs.

"This really hit home, I thought we were going to lose the house," said Titcomb, a native of Nogales, Ariz. "For what, so some guy can smuggle pot or meth?"

Titcomb is frustrated that officials only report such fires as human-caused and ignore the reality that some are likely started by smugglers and illegal immigrants. The political sensitivity of border issues scares politicians from talking about the truth, he said.

One theory percolating in the Tubac/Rio Rico area is that the Murphy Fire was started by two illegal immigrants in distress.

But Titcomb finds that theory hard to believe because all somebody would have to do to get help is walk down from the mountains to the numerous houses nearby. And since it was set in late May, it also seems unlikely it was to keep a group warm.

He believes it's more likely that drug smugglers set a fire in the area to burn Border Patrol sensors, a theory he heard from several firefighters. Most of the Border Patrol agents he sees in the area say they are responding to sensors, he said.

Border Patrol officials declined to discuss the cause of the Murphy Fire, citing the ongoing Forest Service investigation. Judd, of the union, said he hasn't heard of smugglers burning sensors, but said it might be a new tactic.

"It could be effective, sure," Judd said.

Focus on loss, not culprit

The Horseshoe 2 Fire started May 8, about 35 miles north of the U.S.-Mexico border in the Chiricahua Mountains of Southeastern Arizona.

The mountain range and the valleys surrounding it are commonly used by those smuggling drugs and people. Cochise County rancher Robert Krentz was killed in March 2010 on his property south of the fire. The case is still unsolved but authorities believe he was shot by a cross-border smuggler.

The Burro Springs area where the fire started is a popular staging area for smugglers, brimming with backpacks and trash left behind, said Ed Ashurst, who manages the 10X Ranch in the valley east of the Chiricahuas. There are propane tanks used to cook up there, he said. It's rugged, mountainous terrain only accessible by foot or horseback.

"It's frequented by nobody except illegal aliens," Ashurst said. "Virtually everyone down here believes an illegal alien started it (the fire). Who else started it?"

He said he believes the first Horseshoe Fire in 2010 was also started by illegal immigrants but he doesn't expect Forest Service officials to admit that. The Obama administration doesn't want to say it was an illegal immigrant because that would bring into question its claims that the border is more secure than ever, Ashurst said.

Ashurst and others have heard that Border Patrol agents tracked four illegal border crossers to the start of the Horseshoe 2 Fire, and that the first Forest Service firefighters spotted the same tracks, he said.

His fellow ranchers west of Nogales have told him the Murphy Fire was also caused by illegal immigrants.

But few believe the cases will be solved, which is why area resident Cumming thinks it's a waste of energy to focus on who started the fire. The focus should be on what to do about the tremendous loss of mature trees and habitat for thousands of animals, he said.

"This fire has been real devastating," Cumming said. "To sit back and place blame about who caused it is moot."

Contact reporter Brady McCombs at 573-4213 or bmccombs@azstarnet. com. Star reporters Tom Beal and Doug Kreutz contributed to this story.