Zortman said the arrival of the minutemen coincides with a previously planned step-up in enforcement. For now there are about 200 additional agents detailed to Arizona, and eventually the state's Border Patrol will add 534 agents.

Minuteman spokesman Grey Deacon says it's "an absolute falsehood" that any minutemen are setting off the Border Patrol's sensors. He said the Border Patrol assured the minutemen that they weren't in any sensor areas.

The volunteers "are under absolute orders not to go wander around," he said, suggesting the sensors are being tripped by people from the American Civil Liberties Union, which has members in the area monitoring the effort.

The Border Patrol said triggering a sensor would involve more luck than intention because sensor locations are kept secret.

Ray Ybarra, organizer of the ACLU observation, said so far there hasn't been any interaction between the minutemen and migrants. However, he said there are still concerns, as news media attention fades.

"I'm not trying to demonize people and call them all evil racists; it's definitely a fear and concern," Ybarra said. "I hope it's a real fear and concern of the volunteers as well. The border road looks like a smorgasbord for white supremacists to come and recruit."

While some racial slurs were shouted at rallies, Ybarra says, "out here in the desert, to be honest, people have been very nice."

Ybarra says it's unfortunate the minutemen have gotten so much attention, when hundreds of people die crossing the border every year.

"The real focus should be on the needless suffering and death," he said.

Wood says he has sympathy for the border crossers but believes illegal immigrants create too much stress on education, welfare and health systems in his hometown.

"It's really opened my eyes, seeing how the Mexican government treats its own people," he said, referring to the Mexican military, or "federales," who, armed with machine guns, rounded up would-be border crossers "like sheep. . . . It's really sad."

"They are very poor," he said. "Some people have walked 40 to 50 miles. They bring their families."

Earlier, at a nearby post, Alex Segura, a board member of Utah Immigration Reform and Enforcement, had reported what he believed to be 35 would-be border crossers resting under a railroad bridge, waiting for dark to make the final trek of about a mile to the United States.

Segura has manned the border for some 24 hours over the last three days. If anything, the experience has strengthened his resolve to fight for tougher immigration laws in Utah and at the federal level.

"We are a group watching our neighborhood, which is America," Segura said.