The wildfires also have resulted in the destruction of valuable natural and cultural resources in the National Forest System and pose an ongoing threat to visitors, residents and responding firefighters, according to federal law enforcement authorities and others.

In the Coronado National Forest in Arizona, with 60 miles of land along the U.S.-Mexico border, U.S. Forest Service firefighters sent in to battle fires or clear wild land fire areas are required to be escorted by armed law enforcement officers.

Armed smugglers of aliens and drugs have walked through the middle of active firefighting operations, the authorities said.

The Border Patrol’s Tucson, Ariz., sector, which encompasses most of the Coronado National Forest, has the highest incidence of cross-border violators in the nation. Nearly 500,000 illegal aliens were apprehended last year — more than 30,000 a month. In addition, nearly 100,000 pounds of marijuana, with a street value of $200 million, was seized as it was hauled through the Coronado National Forest.

Last month, the Border Patrol — in a single operation targeting illegal aliens causing what Forest Service officials called “significant damage” to the Coronado National Forest — apprehended more than 300 illegals along just a three-mile section of Arizona-Mexico border and confiscated 600 pounds of marijuana in a 10-day period.

At least five fires were set below a Border Patrol observation post during the operation in an effort to burn the agents out, according to a Forest Service report. The fires were extinguished, and no one was arrested.

Wildfires are being set by alien and drug smugglers, authorities said, to create a diversion in an attempt to gain undetected access across the border. The fires correspond to a dramatic rise in assaults against Border Patrol agents — up more than 100 percent over last year.

“Criminal activity by both illegal immigrants and citizens in forests near the border is a threat to members of the public trying to use their public lands and to our employees trying to manage these lands,” Tina J. Terrell, a Forest Service supervisor told a House subcommittee in May.

She said law enforcement personnel have been assaulted, threatened with weapons and shot at, and their vehicles have been rammed by cross-border violators. Because of the remoteness of the area, she said, timely assistance from other law enforcement agencies is not always possible and communications limitations and active interference with radio frequencies in Mexico create additional safety risks.

“Even normal enforcement duties bring our officers in regular contact with cross-border violators,” she said. “Our officers risk their lives every day to enforce the law in these remote federally managed lands.”