A prototype of the Google’s censored search engine for China reportedly “links users’ searches to their personal phone numbers,” which would make it easier for government officials to monitor users’ search history. The Intercept reports that the search engine—codenamed Dragonfly and built for Android devices—would censor any data “deemed sensitive” by the Communist Party regime. A “censorship blacklist” that Google reportedly put together includes the terms “human rights,” “student protest,” and “Nobel Prize” in Mandarin. The engine will also provide weather and pollution data from an “unnamed source in Beijing,” which is worrisome since the Chinese government has a history of manipulating pollution data in cities, The Intercept reports. The search engine would be operated by Google and a company in mainland China, and workers for both entities would reportedly have the ability to update the blacklisted terms, raising concerns that Google executives in the U.S. could “maintain effective control and oversight over the censorship.” On Thursday, 16 U.S. lawmakers sent a letter to Google CEO Sundar Pichai citing “serious concerns” about the project and demanding more information. A number of employees have also quit Google out of protest of the project.