Stephen Shankland/CNET

A prototype for Google's censored search engine in China would reportedly connect users' queries to their phone numbers, making it easier for the government to track their searches.

The engine, reportedly code-named Dragonfly and designed for Android devices, would exclude content that isn't approved by the Chinese government, such as information on democracy, free speech and protests, according to The Intercept.

Sources told the publication that prototypes for Dragonfly link the search app to users' phone numbers, meaning those who search for banned information could be interrogated or detained if security agencies got a hold of Google's search records.

"This is very problematic from a privacy point of view, because it would allow far more detailed tracking and profiling of people's behavior," Cynthia Wong, senior internet researcher with Human Rights Watch, told The Intercept. "Linking searches to a phone number would make it much harder for people to avoid the kind of overreaching government surveillance that is pervasive in China."

Dragonfly has received pushback from Google's workforce. About 1,000 employees are protesting the project, and some people are reportedly leaving the company altogether.

"We've been investing for many years to help Chinese users, from developing Android, through mobile apps such as Google Translate and Files Go, and our developer tools," Google said in a statement in response to a request for comment. "But our work on search has been exploratory, and we are not close to launching a search product in China."

On Thursday, a bipartisan group of 16 lawmakers sent a letter to Google asking if its work in China meant the search giant would comply with China's internet censorship and surveillance policies.