How did the epidemic in Baoji caijiapo come about?

Come back from outside the province. According to relevant data, 3 cases of asymptomatic infection in Baoji were all from Xinjiang. Case 1 returned to Baoji by z 136 from Urumqi. Cases 2 and 3 drove home from Xinjiang, got off the caijiapo Expressway and were transferred to the isolation point for closed-loop isolation the next day.