At least 127 people were killed and 1,294 missing due to a rain-triggered landslide, which hit Zhouqu county in China's Gansu province on Sunday morning.
Around 76 people were injured and rescuers were racing against time to dig out survivors from crushed homes, the Chinese Ministry of Civil Affairs said.
"Torrential rains began to fall at around 10 pm on Saturday. Then there were mudslides and many people became trapped. Now sludge has become the biggest hindrance to rescue operations. It's too thick to walk or drive through," said Diemujiangteng, head of the county.
The clogged river in the narrow valley spilled over its banks, triggering floods and mudslides that hit the town after midnight. The disaster shattered a small hydro station and left more than 100 people dead, Xinhua reports.
The landslide flattened a five kilometers long area. "Most of the 2,000 people living in the area failed to escape in time and were drawn into the mud," authorities from the Gannan Tibetan autonomous prefecture, which administers Zhouqu, said.
Pu Junli, a military official who led rescue efforts, said the sludge was "too massive, mostly as thick as one meter".
The Ministry of Public Security on Sunday activated its emergency response mechanism to organize about 1,000 firefighters and special police in nearby areas to head for the affected area to rescue victims, the ministry posted on its website.