The Border Patrol says the arrests at a humanitarian aid camp of four men suspected of crossing the border illegally do not signal a change in policy, although activists disagree.

The humanitarian aid group No More Deaths said about 30 Border Patrol agents, along with 15 trucks and a helicopter, executed a search warrant Thursday on the group’s camp in Arivaca.

Volunteers with No More Deaths say the arrests mark a “targeted attack” on humanitarian aid workers, while an agency spokesman said the Border Patrol has not changed its policies.

The camp itself is a collection of about a dozen makeshift structures, all of which are on a parcel of private property, that has grown bit by bit over the last decade. A recreational vehicle serves as the office, solar panels power a refrigerator, and a couple dozen beds, some of which are supported by green milk crates, are tucked inside large tents.

The purpose of the camp is to help border crossers recover from exposure to the elements, heal blistered feet, or get rid of sickness after drinking contaminated water from cattle tanks.

The arrests came Thursday when agents, looking for four Mexican men whose footprints they had tracked for 18 miles, served a search warrant on the camp.

For the No More Deaths volunteers at the camp, the men were patients seeking medical help after enduring triple-digit temperatures in a trek through the desert. For the Border Patrol agents, they were suspected illegal immigrants who had violated federal law.

The June 15 search warrant signed by U.S. District Magistrate Judge D. Thomas Ferraro authorized the Border Patrol to seize any individuals at the camp who were in the country illegally, including four people depicted in “photographs taken by a sensor at 4:25 p.m. on June 13, 2017,” according to a copy of the warrant provided by No More Deaths.

The arrests two days after the sensor took photos of the men raised questions as to why the agents didn’t arrest them before they arrived at the camp or after they left.

Agents would have arrested the men before they entered the camp, Border Patrol spokesman Agent Vicente Paco said, but they were “following footprints” and agents did not catch up with them before they arrived at the camp.

Agents waited for two days outside the camp and contacted the camp operators, but the four suspected illegal immigrants did not emerge, Paco said.

No More Deaths spokeswoman Maryada Vallet said Thursday’s search was the first time agents had entered the camp with a warrant. She cited a 2013 agreement with the Border Patrol not to interfere with humanitarian aid efforts.

The Border Patrol’s search of the camp showed a “palpable difference” from how an encounter with the agents played out weeks before, long-term volunteer Tim Juge told the Star during a visit to the camp Friday.

“The type of operation they are doing, for me, is unprecedented and there’s nothing routine about what they did,” Catherine Gaffney, a longtime volunteer who was present during the arrests, told The Associated Press. “It wasn’t part of their day-to-day operation. It was a staged military siege on our camp.”

In late May, eight border crossers arrived at the camp seeking medical help. Similar to this week’s incident, agents had tracked them to the camp and asked that they be sent out.

After volunteers told them what was happening, the border crossers decided to turn themselves in to the Border Patrol, Juge said.

On Thursday, “the patients decided they did not want to turn themselves in,” he said, adding: “We respect whatever choice people make once we’ve done everything we can to inform them.”

The Border Patrol said in a news release that two of the men arrested in May had criminal histories. Paco could not provide information about their convictions.

One of the men arrested Thursday previously was convicted of smuggling more than 600 pounds of marijuana, the agency said in a news release Friday.

The Border Patrol’s Tucson Sector has not changed how it deals with humanitarian aid groups, Paco said. He disputed that the agency has an agreement with No More Deaths not to interfere with aid efforts.

Instead, he said “guidance” from Tucson Sector management directs agents not to interfere with water stations or “actively surveil” humanitarian aid facilities or camps.

However, if probable cause exists to believe illegal activity is occurring at the facility or camp, then agents will apply the law as it is stated, Paco said.

He said the Border Patrol understands No More Deaths’ mission to provide aid, but added that those efforts can encourage smugglers.

Contact reporter Curt Prendergast at 573-4224 or cprendergast@tucson.com or on Twitter @CurtTucsonStar