Last month, it was revealed that Google was offering its resources to the US Department of Defense for Project Maven, a research initiative to develop computer vision algorithms that can analyze drone footage. In response, more than 3,100 Google employees have signed a letter urging Google CEO Sundar Pichai to reevaluate the company’s involvement, as “Google should not be in the business of war,” as reported by The New York Times.

Work on Project Maven began last April, and while details on what Google is actually providing to the DOD are not clear, it is understood that it’s a Pentagon research initiative for improved analysis of drone footage. In a press statement, a Google spokesperson confirmed that the company was giving the DOD access to its open-source TensorFlow software, used in machine learning applications that are capable of understanding the contents of photos.

Google has described its work on Project Maven as “non-offensive,” and Diane Greene, the head of Google’s cloud operation who sits on Alphabet’s board of directors, said the technology will not be used to “operate or fly drones” and “will not be used to launch weapons.” But this is not enough for the many employees who signed the letter addressed to Pichai. “While this eliminates a narrow set of direct applications,” the letter reads, “the technology is being built for the military, and once it’s delivered it could easily be used to assist in these tasks.”

“This contract puts Google’s reputation at risk and stands in direct opposition to our core values.”

The letter goes on to ask that Google stop its involvement in Project Maven and that the company create and enforce a policy stating that it will not engage in building warfare technology. “This contract puts Google’s reputation at risk and stands in direct opposition to our core values,” the letter states. “Building this technology to assist the US government in military surveillance — and potentially lethal outcomes — is not acceptable.”

A Google spokesperson issued a response to the letter on Tuesday, reports The New York Times, stating that “any military use of machine learning naturally raises valid concerns ... We’re actively engaged across the company in a comprehensive discussion of this important topic.” Additionally, “The technology is used to flag images for human review and is intended to save lives and save people from having to do highly tedious work,” reads Google’s statement.

Other companies, such as Amazon and Microsoft, have also worked on defense projects, but the Google employees backing the letter don’t see this as a way to endorse Google’s work on Project Maven. “Google’s unique history, its motto ‘Don’t Be Evil,’ and its direct reach into the lives of billions of users set it apart,” the letter states. In the past, Google has been careful about ties to military research. In 2013, it rejected funds from the Defense Advanced Research Projects Agency (DARPA) after buying up a string of robotics companies with ties to the military research organization.