More than 400 Google staffers have signed an open letter urging Google to cancel an in-development censored version of Chinese search app.

The letter was published on Tuesday (Nov 27) with over 400 signatories, most of which are software engineers. It follows an internal letter, which garnered 1,400 signatures earlier this year, reports the verge.

The letter opposes Project Dragonfly, a China-focused version of Google search that would reportedly block certain search terms and make it easy for the government to monitor users’ searches. Google has repeatedly declined to comment on Dragonfly, saying that its work is ‘exploratory’ and that it is ‘not close to launching a search product in China.’

Dragonfly has drawn criticism from US Vice President Mike Pence who condemned it last month. It’s also garnered opposition within Google where employees say company executives have ignored their concerns.

“Our opposition to Dragonfly is not about China, we object to technologies that aid the powerful in oppressing the vulnerable, wherever they may be,” the letter says.

“Dragonfly in China would establish a dangerous precedent at a volatile political moment, one that would make it harder for Google to deny other countries similar concessions,” it added.