The recent whereabouts of the two COVID-19 cases in Horgos City, northwest China's Xinjiang Uygur Autonomous Region, have been fully revealed, but the exact source of the infections is still under investigation, local officials said in a press conference on Monday.

"Horgos sits on the country border and the situation can be complicated," said Wang Shujiang, deputy head of health in the city, adding that the two people didn't visit any risky areas or contact any infected cases in the recent two weeks.

The two infected people, who were found to be infected by the novel coronavirus on Sunday, showed no symptoms.

Meanwhile, a second round of nucleic acid tests is being conducted across the city. The local government also deployed staff to disinfect the areas where the two people have been recently.

Horgos Deputy Mayor Li Junyi told media members in Urumqi via video link that the government has set up 142 testing sites in the city.

"We planned to test 38,376 people in the first round," she said. "As of 10:00 a.m., October 4, the results have all come out and all of them are negative."