Hundreds of Amazon employees have signed a letter opposing the company's decision to sell its facial recognition software to law enforcement.

More than 450 employees signed a letter addressed to CEO Jeff Bezos and other Amazon executives demanding that the company Palantir be banned from Amazon Web Services and that Amazon implement employee oversight for ethical decisions, according to one of the employees who signed the letter . Palantir is the software firm the operates much of Immigration and Customs Enforcement's deportation and tracking program.

The employee said the letter's signatories are concerned that "Amazon is designing, marketing, and selling a system for dangerous mass surveillance right now."

"Amazon's website brags of the system's ability to store and search tens of millions of faces at a time," the employee said in a post on Medium. "Law enforcement has already started using facial recognition with virtually no public oversight or debate or restrictions on use from Amazon."

The facial recognition software, Rekognition, is already being used by law enforcement in Orlando, Florida, to compare photos to a database of mugshots. Amazon has also recommended using the software with officer body cameras.

According to the anonymous source, other employees "were disappointed" when Teresa Carlson, vice president of the worldwide private sector of Amazon Web Services, said that the company "unwaveringly supports" law enforcement, defense and intelligence customers, despite not knowing "everything they're actually utilizing the tool for."

The employee wrote that "selling this system runs counter to Amazon's stated values." In July, the American Civil Liberties Union conducted a test using Rekognition. The organization uploaded 10,000 mugshots into the software and cross-references photos of each member of Congress. The tests resulted in 28 false matches, a disproportionate number of which involved people of color.

"The product we're selling is a flawed technology that reinforces existing bias. … The existing biases ... exist within wider society and our justice system. The use of facial recognition will only reproduce and amplify existing systems of oppression," the employee wrote.