People with close contact with a new asymptomatic coronavirus carrier and those in places adjacent to the carrier's home and workplace have all tested negative after the case was found in Guangzhou, Guangdong province, on Saturday.

Forty-two-year-old Xu, who delivered meals and cleaned rooms at quarantine property Tokai Hotel in Yuexiu district, is believed to be infected when collecting trash at door of a room on Wednesday afternoon due to accidental exposure, said Zhang Zhoubin, deputy director of the Guangzhou disease control and prevention center, at a news conference in Guangzhou on Sunday.

The nucleic acid sequence of the coronavirus Xu is infected with is identical with that of the Delta variant tested in Yang, who came from overseas and was confirmed a COVID-19 patient on Saturday.

Xu had been living in the hotel after August 30 and the risk of transmission in the community is low, said Chen Bin, deputy director of the Guangzhou health commission. Xu is under medical observation at Guangzhou Eighth People's Hospital.

Fifty-six people are working at Tokai Hotel where 103 people are being quarantined. Since August, seven imported infection cases have been reported in the hotel.

Massive nucleic acid tests were carried out in subdistricts including Jianshe, Hongqiao, Dongshan, Huale and Dengfeng in Yuexiu district. By midnight on Saturday, all the 92,185 samples collected had tested negative.

By 10 am on Sunday, 97,878 samples had been collected in Yuexiu, said Guo Huan, deputy chief of the district, adding Tokai Hotel and some adjacent buildings have been put under control.

Because Xu stayed at home in Haizhu district and moved around home on August 28 and 29, the building where her home is located and some adjacent buildings were locked down, said Fu Xiaochu, deputy chief of Haizhu. A total of 35,293 samples from people in Haizhu district have all tested negative,.

All people with close contact with Xu have been put under medical observation at designated places.

The mutations of the coronavirus have posed huge challenge to epidemic control and the risk of imported infections have kept growing in Guangzhou, Chen said.