Immigrants’ rights advocates have filed a Freedom of Information Act (FOIA) request for records related to migrant deaths along the southern US border.

In a letter sent to the Department of Homeland Security (DHS) and Customs and Border Protection (CBP) on Friday, advocacy groups No More Deaths and the Center for Constitutional Rights expressed particular concern about the increasing number of migrants attempting to cross the border in undesignated areas as a result of new limitations at official ports of entry. According to a September 2018 report from the DHS Office of Inspector General, referenced in the groups’ request letter, the Trump administration has imposed restrictions on the asylum process at ports of entry despite having publicly encouraged asylum-seekers to go to those locations.

The request letter specifically focuses on deaths of migrants traveling through the harsh terrain surrounding Tucson, Arizona. Noting that area law enforcement agencies frequently refer 911 calls from migrants directly to the Border Patrol, the advocacy groups requested “all records related to the Border Patrol’s practice of assisting migrants through search and rescue operations in the Tucson Sector.” In addition to data regarding emergency calls and responses, the groups have asked for policy and procedure documents as well as information about cooperation agreements between the Border Patrol and local law enforcement agencies that coordinate emergency services.

Explaining the seriousness of the issue of migrant deaths, the groups referred to a 2016 report by the International Organization for Migration (IOM). In that document, researchers wrote that most migrants attempting to cross the southern US border “die from exposure to the elements” while “a considerable number drown in the Rio Grande each year … [and] others may die in violent incidents, or may fall ill and be left in the desert.” According to the IOM, “at least 320” migrants died along the border in 2015. The IOM report observes that the Border Patrol itself estimated that between 1998 and 2015, the number of migrant deaths ranged from 250 to 500 every year.

No More Deaths and the Center for Constitutional Rights have asked for expediting processing of their request, citing DHS regulations that enable requestors to obtain faster responses when “the lack of expedited treatment could reasonably be expected to pose an imminent threat to the life or physical safety of an individual” and where there exists “an urgency to inform the public about an actual or alleged federal government activity.” DHS must respond within 10 calendar days of receiving the request. Agency regulations further require that where a request for expedited processing is granted, it “shall be given priority and shall be processed as soon as practicable.”