In the wake of protests from Google and Microsoft workers, who objected to their employers’ contracts with the Pentagon and U.S. Immigration and Customs Enforcement (ICE), employees at Amazon are circulating a letter to CEO Jeff Bezos, urging the billionaire to stop selling facial recognition software to law enforcement and remove the big data firm Palantir from its cloud.

In a letter published by Gizmodo, the Amazon workers voice their concern that these surveillance technologies will be misused, particularly to target marginalized groups. They reference an investigation from May, in which the American Civil Liberties Union showed that Amazon had marketed its facial recognition software, Rekognition, which can identify and track faces in real time, to police departments around the country.

“We don’t have to wait to find out how these technologies will be used,” they write. “We already know that in the midst of historic militarization of police, renewed targeting of Black activists, and the growth of a federal deportation force currently engaged in human rights abuses — this will be another powerful tool for the surveillance state, and ultimately serve to harm the most marginalized. We are not alone in this view: More than 40 civil rights organizations signed an open letter in opposition to the governmental use of facial recognition, while over 150,000 individuals signed another petition delivered by the ACLU.”

The letter follows demands by Google and Microsoft workers, who put pressure on their employers to cut ties with the Pentagon and ICE, respectively. In April, more than 4,000 Google employees signed an open letter to CEO Sundar Pichai, calling for the company to end its affiliation with Project Maven, a controversial program that seeks to automatically classify images of people from drone footage to speed up the rate of analysis. In May, about a dozen employees resigned. The protests resulted in Google announcing plans to end its involvement. Microsoft faced similar pressure this week over contracts that provide its Azure cloud platform to ICE.

Beyond revoking the sale of facial recognition software to law enforcement, the Amazon workers have urged Bezos to remove Palantir, a predictive policing company founded by Peter Thiel, from Amazon Web Services (AWS). Palantir enjoys a large contract with ICE.

“We also know that Palantir runs on AWS,” the letter reads. “And we know that ICE relies on Palantir to power its detention and deportation programs. Along with much of the world we watched in horror recently as U.S. authorities tore children away from their parents. Since April 19, 2018 the Department of Homeland Security has sent nearly 2,000 children to mass detention centers. This treatment goes against U.N. Refugee Agency guidelines that say children have the right to remain united with their parents, and that asylum-seekers have a legal right to claim asylum. In the face of this immoral U.S. policy, and the U.S.’s increasingly inhumane treatment of refugees and immigrants beyond this specific policy, we are deeply concerned that Amazon is implicated, providing infrastructure and services that enable ICE and DHS.”