Firefighters say the presence of illegal immigrants in border areas and fear for their safety keeps them from utilizing their full arsenal for stopping wildfires in the Arizona border region, according to a recently released Government Accountability Office (GAO)report.

Wildfires can come from both natural and human causes, but human-caused fires are of particular concern in Arizona. The GAO was asked toexamine the extent that people crossing the border illegally were the cause of wildfires and how the presence of travelers in those areas impacted fire suppression activities. The GAO interviewed officials from several agencies including the U.S. Forest Service, the Department of Agriculture, and the National Interagency Fire Center.

The GAO found that there were 422 human-caused wildfires in the Arizona border region from 2006 to 2010. Of the 422 fires, only 77 were investigated. Illegal border crossers accounted for 30 of those fires, according to investigators.

All 30 of the fires were found within 40 miles of Arizona’s border with Mexico – some along known smuggling routes. In many cases investigators found discarded bottles or food with Spanish labels, evidence they say points to illegal border crossers. Additionally, a GAO review of 1,123 incident reports included 57 comments by firefighters who suspected fires were started by illegal border crossers.

Officials expressed concern for both the safety of their firefighters and for people crossing the border in these areas because of fire suppression techniques and delays caused by unexpected encounters.

While the Horseshoe Two fire burned 223,000 acres in June, evidence showed that drug traffickers continued using smuggling routes in the area, according to one report. There are no documented cases of firefighters encountering smugglers, but agencies told the GAO that they worried violence could result if firefighters did encounter armed smugglers while fighting fires in remote areas.

Officials also worry that illegal border crossers could be killed or injured when firefighters start backfires to control wildfires. Firefighters will often have Customs and Border Protection (CBP) check an area first before starting backfires, but the “additional step can increase the resources and time needed to suppress the fire.”

They’ve also reduced nighttime firefighting activities because of the “perceived threat to firefighters’ safety.” One Forest Service official told the GAO that firefighters were unable to set up overnight camp on the first day of a fire in 2009 because no law enforcement was available to provide security.

Firefighters working with the forest service are told not to use their radios when they encounter border crossers because of fear that the travelers may think they are being reported and react violently, one official told the GAO. And in some areas, radios may not be of much use anyway because “illegal border crossers may use the same radio frequencies as firefighters, causing interference and limiting their ability to safely coordinate fire suppression activities,” according to Federal and tribal officials.

Both government agencies and the GAO say there are shortfalls in getting accurate numbers on the impact of border crossers on wildfires. Investigations were based on the availability of fire investigators rather than the size or locations of fires.

“The total number of fires ignited by illegal border crossers on federal lands in the Arizona border region is not fully known, in part because federal land management agencies have not conducted investigations of all human-caused wildland fires that occurred on these lands, as called for by agency policy,” the reported concluded.

The policy, the Interagency Standards for Fire and Fire Aviation Operations, requires in-depth investigations of any fires determined to be caused by humans. Forest Service officials told the GAO that they lacked trained fire personnel to investigate the fires in-depth.

At a press conference addressing Arizona’s wildfires in June, Senator John McCain (R-AZ) raised eyebrows when he suggested thatillegal immigrants were the cause of Arizona’s wildfires. McCain said, after being briefed by Forest Service officials, that many fires were caused by travelers trying to keep warm, signal others, or distract law enforcement. Critics accused McCain of trying to use the wildfires to push his own immigration agenda. McCain said that as far back as 2006 Forest Service officials had warned of cooking and warming fires being set by illegal border crossers.

“Armed smugglers havewalked through the middle of active firefighting operations… [They] must now send armed officers to clear wildland fires areas or provide security for firefighters,” he told ABC News, referring to the Horseshoe Two fire. “The agencies have taken some steps to mitigate the risks to firefighters by, for example, using law enforcement to provide security,” the GAO report confirmed. “However, none of the agencies have developed or implemented a risk-based approach for addressing these challenges.”