National Guard troops working at an observatory post near Sasabe were approached by a group of armed individuals late Wednesday night and forced to flee, said Border Patrol and National Guard officials Thursday.
The event occurred about 11 p.m. Wednesday at one of the National Guard entrance identification team posts near Sasabe, said National Guard Sgt. Edward Balaban. The troops withdrew safely. No shots were fired and no one suffered injuries, he said.
"We don't know exactly how many because obviously it took place in the dark," Balaban said. "Nobody was able to get an accurate count."
Border Patrol officials are investigating the incident and trying to determine who the armed people were, what they were doing and why they approached the post. The incident occurred in the west desert corridor between Nogales and Lukeville in the vicinity of Sasabe, Balaban said.
The Guard troops are not allowed to apprehend illegal entrants.
"We don't know if this was a matter of somebody coming up accidentally on the individuals, coming up intentionally on the individuals, or some sort of a diversion?" said Rob Daniels, Border Patrol Tucson Sector spokesman. "We just don't know and that's why everything's got to be looked into."
Border Patrol officials say the armed group returned to Mexico, Daniels said.
The west desert corridor — where the incident occurred — has been the busiest in the Tucson Sector for marijuana seizures since last year. Agents have seized 124,000 pounds of marijuana there since Oct. 1, said Rob Daniels, Border Patrol Tucson Sector spokesman. Sector wide, marijuana seizures are up 28 percent this fiscal year, according to agency figures.
With more Border Patrol agents and National Guard troops patrolling the Arizona section of the U.S.-Mexican border, it has become more difficult to smuggle drugs and people across, Daniels said.
"That heightened frustration may have been connected to what took place last night," Daniels said.
Officials will make a decision about whether changes need to be made in regard to the entrance identification teams following the investigation, Balaban said.
Since arriving in mid-June, the Guard has assisted the Border Patrol by manning control rooms, doing vehicle and helicopter maintenance, repairing roads and fences and constructing vehicle barriers and fences, and spotting and reporting illegal entrants in entrance identification teams.
There are dozens of National Guard entrance identification teams along the Mexican border, including east and west of both Nogales and Sasabe and on the Tohono O'odham Nation. The troops stand post on hilltops next to army-green tents and serve as extra eyes and ears for the Border Patrol.
"Having any of them breached could have been very, very unsafe," Daniels said. "Not just for the National Guardsman, but for any of our personnel in the area as well."