BEIJING/LANZHOU - Fifteen people have been confirmed dead and 28 remain missing as of 6 pm on Saturday after flash floods struck Yuzhong county and surrounding areas in Lanzhou, Gansu province, said the provincial flood control and drought relief headquarters, as reported by China Central Television.

Torrential rainfall from Thursday to Friday triggered the disaster, damaging roads, power lines, and other infrastructure. The rain began pounding Yuzhong, which is under the jurisdiction of the provincial capital of Lanzhou, as well as other areas of Lanzhou, with precipitation reaching 220.2 millimeters by noon on Friday.

The floods severely disrupted sections of the S104 highway between Xinglong Mountain in Wanjiazhuang village and Xiakou in Chengguan township, as well as the entire Xinghuang road, with a combined damaged length of nearly 40 kilometers, according to the local authorities.

The routes are vital transport links for goods and people in Yuzhong and nearby areas. Their closure has hampered relief operations and daily travel.

As of 6 pm on Friday, the provincial transport authorities have deployed more than 40 pieces of heavy machinery and over 200 emergency workers, restoring traffic at three damaged sections of the S104 highway and four on Xinghuang road.

Search and rescue efforts and infrastructure repairs are underway. As of 6 pm Saturday, all roads leading to the affected villages in Yuzhong had been cleared, said the provincial transport department. Power supply has been restored in 80 percent of the affected areas.

So far, a total of 9,828 people in Yuzhong have been relocated to safe areas.

ALSO READ: Hundreds evacuated in Gansu after severe flooding

Chinese Vice-Premier Zhang Guoqing has called for all-out efforts to search for people missing in mountain torrents, when directing emergency response work at the disaster site.

Zhang, also a member of the Political Bureau of the Communist Party of China (CPC) Central Committee, left for Yuzhong county on Friday evening to guide on-site search and rescue and emergency response work. He visited the hardest-hit villages of Maliantan and Jiuzhuanggou, as well as a hospital and multiple temporary shelters for relocated residents.

At the on-site command center, Zhang chaired a meeting on rescue and relief operations, stressing that the search for those who are missing remains the top priority and urging rescue workers to move as quickly as possible while taking precautions against secondary disasters.

He stressed the need for meticulous care for the injured and compassion towards victims' families, directing authorities to ensure adequate living conditions for all relocated residents.

Repairs to damaged transportation, telecommunications and power infrastructure should be accelerated, he added.

Given recent, repeated extreme weather events, Zhang urged enhanced accuracy in rainfall forecasting, close monitoring of areas vulnerable to mountain torrents and geological hazards, and prompt relocation of at-risk residents.

"After receiving the rainfall alert at 4 pm Thursday, our entire staff immediately conducted door-to-door notifications, warning residents to take precautionary measures and convincing camping tourists in vulnerable areas to evacuate," said Zhang Kefu, Party secretary of Yaogou village, who has been working on the relocation of affected residents.

"In all my years, I've never witnessed such a heavy rain. Stones as big as beds rushed down from the riverway. I stayed awake all night in my room, too terrified to close my eyes," 84-year-old Hao Xiuying told Xinhua from a relocation hotel.

Gansu issued alerts for mountain torrents and geological disasters on Saturday evening as rainstorms are still expected in many parts of the province.

ALSO READ: Three missing after flooding in Gansu

At 6 pm Saturday, an orange alert - the second-highest alert level in China's four-tier system - for mountain torrents was issued by the provincial department of water resources and the provincial meteorological bureau, warning of potential mountain torrents in the Gannan Tibetan autonomous prefecture, Dingxi city and Longnan city from 7 pm Saturday to 7 pm Sunday.

Additionally, at 7:30 pm Saturday, the provincial department of natural resources and the provincial meteorological bureau issued an orange alert for geological disasters, forecasting potential disasters such as collapse, landslide and mudslide in Yuzhong county in Lanzhou, Zhouqu county in the Gannan Tibetan autonomous prefecture, Anding district and Lintao county in Dingxi city, and Longnan city from 8 pm Saturday to 8 pm Sunday.

Emergency response for flood control

Also on Saturday, the Ministry of Water Resources activated a Level IV flood-control emergency response for five provincial-level regions, as heavy to torrential rains are predicted to sweep across vast parts of the country in the coming days.

From Aug 9 to 11, intense rainfall is expected to batter Henan, Hubei, Chongqing, Sichuan, Shaanxi, Anhui, and Gansu, where the alert was already in place, with some areas facing extreme downpours.

The downpours may cause sharp water level rises in the upper and middle reaches of the Yangtze and Huaihe Rivers, while some small and medium-sized rivers in high-risk areas could exceed warning levels.

The ministry has urged local authorities to step up real-time monitoring of rainfall and river conditions, issue timely public alerts, and enhance urban waterlogging-prevention measures.

Special emphasis should be placed on mitigating risks in smaller rivers and ensuring early evacuations of residents in dangerous areas, according to the ministry.

The State Flood Control and Drought Relief Headquarters on Saturday initiated a Level-IV emergency response for flood control in the provincial-level regions of Jiangsu, Anhui, Hubei, and Chongqing.

The headquarters' office has dispatched work teams to Anhui and Hubei to assist and guide flood control efforts, according to the Ministry of Emergency Management.

READ MORE: Rivers in North, Northeast China pose high flood risk in August

On Saturday evening, the Ministry of Water Resources and the China Meteorological Administration jointly issued an orange alert for mountain torrents in parts of Henan, Hubei and Sichuan from Saturday night to Sunday night, noting that such disasters could also occur in other regions due to heavy rainfalls and urging local authorities to strengthen real-time monitoring, flood prevention alerts and precautionary evacuations.

China has a four-tier weather warning system, with red representing the most severe warning, followed by orange, yellow and blue.