Dozens of Chinese firms have built software that uses artificial intelligence to sort data collected on residents, amid high demand from authorities seeking to upgrade their surveillance tools, a Reuters review of government documents shows.

According to more than 50 publicly available documents examined by Reuters, dozens of entities in China have over the past four years bought such software, known as "one person, one file." The technology improves on existing software, which simply collects data but leaves it to people to organize.

"The system has the ability to learn independently and can optimize the accuracy of file creation as the amount of data increases. (Faces that are) partially blocked, masked, or wearing glasses, and low-resolution portraits can also be archived relatively accurately,” according to a tender published in July by the public security department of Henan, China’s third-largest province by population.