Beijing, Dec 13: Chinese authorities are collecting D samples, fingerprints and other biometric data of millions of people in the country’s far western Xinjiang region, Human Rights Watch (HRW) said in a report on Wednesday. Officials are also building a database of eye scans and blood types of everyone aged between 12 and 65 in the region, adding to controls in a place some experts called an “open-air prison”, the Guardian reported. The data can be used for “surveillance of persons because of ethnicity, religion, opinion or other protected exercise of rights like free speech”, Human Rights Watch said.