Genome sequencing analysis of 20 samples collected from recent COVID-19 infections in Hunan province showed they were similar to sample in the outbreak in Nanjing, Jiangsu province, and have been identified as the Delta variant, the Hunan Center for Disease Control and Prevention was reported as saying on Monday by Hunan Daily.

According to Nanjing health authorities, the recent COVID-19 outbreak in the city originated from an imported case on Flight CA910 from Russia on July 10.

"The sample analysis uses several procedures, including use of both the second and third generation of sequencing techniques, to analyze the gene sequence and ensure accurate results," said Zhan Zhifei, director of the Hunan CDC's clinical laboratory.

In addition, 13 temporary testing labs are being built in Zhangjiajie, Hunan, to boost capacity. Zhangjiajie has reported the most local confirmed cases in the province since the outbreak. As of Sunday, seven facilities had entered service.

Hunan has reported 19 local confirmed cases of COVID-19 since the first case was detected on July 20.

Zhu Youfang contributed to this story.