Tianjin reported no positive coronavirus tests for all residents in its Binhai New Area and the alert level in several sections in the area will be downgraded, officials said on Tuesday.

"The area started to conduct universal screening Saturday morning among the 2,467,411 residents and finished sample collection work on Monday evening," Liang Chunzao, deputy director of Binhai New Area, said at a Tuesday night news conference. "All testing results reported on Tuesday morning came back negative for the coronavirus."

A pig head imported from North America was confirmed as the source of the recent COVID-19 outbreak in Tianjin, said Zhang Ying, deputy head of the Tianjin Centers for Disease Control and Prevention.

"According to the current epidemic situation, the alert in the medium-risk regions, Hangu Street, Block A and B of the cold-chain logistics area in the central fishing port in Binhai New Area, will be downgraded to low risk beginning Wednesday," said Gu Qing, deputy director of the city's health commission.

"However, residents should also stick to good habits, including maintaining good hygiene and avoiding gatherings. It is necessary to wear masks and go to a hospital immediately when having symptoms, including fever, physical weakness and dry cough,"Gu said.