If he is taken to the Xishan Detention Center in Urumqi, it should be criminal detention. Xishan is a detention center, not a detention center. You can go to the public security organ to ask about his specific situation. If a person is detained in criminal detention, the public security organ shall serve a notice of criminal detention on his family members. Now he is being held in Xishan detention center, which means he is suspected of some kind of crime. Once in criminal detention, his family will never see him again. It is suggested to entrust a lawyer to provide legal help immediately and let him meet at the detention center to understand the specific situation.