Survivors grieve over family members and homes lost in the disaster on August 8, 2010.
The China National Committee for Disaster Reduction, the State Flood Control and Drought Relief Headquarters and the Ministry of Civil Affairs lifted the national disaster relief response level to grade II, the second-highest level.
President Hu Jintao and Premier Wen Jiabao instructed Gansu provincial authorities and other related departments to spare no effort to save lives. Wen arrived at Zhouqu county at 4:35 pm to oversee on-site rescue work.
The landslide also damaged the county's water supply system and severely affected essential rice, flour and oil shops, resulting in a shortage of instant foodstuff and drinking water for residents, the local government said.
The county will need 10,000 tons of water and 500 tons of instant food supplies in the next 25 days, after which life is expected to return to normal, a county spokesman said.
Troops were also preparing explosives to blast away the mud and rocks that have choked the Bailong River. The mud and rocks created a backlog of water 3 kilometers long and 100 meters wide, Xinhua reported.
Premier Wen told officials to develop a plan as soon as possible to unblock the river safely.
Authorities from the two neighboring counties of Longnan city at downstream of the river also evacuated 19,000 people on Sunday.
But local conditions hampered rescue work, authorities said.
"Since excavators can't reach the affected site, we can only use spades and our hands to reach those buried," Niu Yongfu, deputy chief of staff with the Gansu Headquarters of the Chinese People's Armed Police Force, told China Daily on Sunday evening.
"It's very hard to locate the people washed away by floods," he said.
Feng Lei, 44, a local doctor whose house was inundated by floodwaters, told China Daily that "the wind and rain was not strong when the landslide arrived, but the water was raging".
"People were screaming for help, some were washed away in just seconds," he said.
The Gansu Electric Power Corporation said two-thirds of the county's power was out. Some communications links were also reportedly down because of the power outage.
The State Grid Corporation later sent 150 people with electricity generators to the site. The first batch of 35 workers arrived at the county seat at about 12:40 am.
By 4:14 pm, power supply was restored to some parts of Zhouqu county, including temporary housing areas, hospitals, two middle schools and communications base stations .
Roads at the outskirts of Zhouqu also reopened after they were blocked by the mudslides, the provincial administration bureau of highways said.
Shen Gang and Xinhua contributed to this story.