Customs and Border Protection officers have raided a medical aid camp run by a non-profit for immigrants in the Arizona desert.
The group No Mas Muertes (No More Deaths) has operated the facility several miles north of the Mexican border since 2004, according to Fox News.
CBP officials say they attempted to engage in talks with staff at the camp to secure four undocumented immigrants, but the talks reportedly proved unsuccessful.
The raid was carried out on June 15 by armed officers, helicopters and trucks.
"The raid on the medical aid camp is unacceptable and a break in our good faith agreements [with] BP to respect the critical work of #NoMoreDeaths," the aid organization wrote on Twitter.
But CBP contended it felt "compelled to seek a search warrant."
Border agents detained four men during the raid, and a similar raid last month resulted in eight arrests.
Eva Lewis, a volunteer with the aid organization, insisted that No More Deaths did not hand the eight immigrants over to CBP in the previous incident.
"They made the decision to turn themselves into custody, that is not the same as anyone turning anyone else into law enforcement," Lewis told BuzzFeed. "Sometimes people decide to go into custody for a variety of reasons. When they make that decision we talk with them about the possibilities of applying for asylum and the risks of going through operation streamline."
The four men were receiving medical care at the camp, which had been placed under increased surveillance in the days leading up to the action.
No More Deaths reports that many immigrants are avoiding seeking aid at the camp for fear of being detained by officers.
The medical aid camp provided an unsigned copy of the agreement it had with CBP to BuzzFeed. The deal stated that the non-profit would be allowed to give medical care to immigrants without being interfered with.
It also guaranteed that CBP officers would be trained in "the Red Cross Code of Conduct, the principles of our relationship, and respect for the independent mission of the humanitarian organization."
The group said CBP informed them that it had been tracking the immigrants for 18 miles as they crossed the border, but arrested them when they were in the camp being treated.
Maryada Vallet, a spokesperson for No More Deaths, said the raid "feels like a direct and targeted attack on the humanitarian assistance [the camp is] providing during these hot and deadly days."
Sources: Fox News, BuzzFeed / Photo credit: Gerald Nino via U.S. Dept. of Homeland Security/Wikimedia Commons