WHO investigation 'must conform' to China's prevention measures

"All these activities must be in accordance with the principle of tracking the origin scientifically and with the ultimate goal of preventing future risks and protecting the safety and health of the people," Zhao told a regular briefing on Thursday.

The mission has been plagued by delays, concern over access and bickering between China and the United States, which has accused China of hiding the extent of the initial outbreak and criticised the terms of the visit, under which Chinese experts conducted the first phase of research.

The team left the hotel shortly after 3 p.m. without speaking to journalists, who were kept at a distance behind yellow barriers, and boarded a bus, whose driver wore full protective gear, and headed to another hotel.