Rescue crews were desperately trying to reach survivors of a devastating landslide in northwestern China Sunday after floodwaters sent mud and debris crashing into a small town, killing 127 people.

Officials say about 2,000 people are still missing in the town of Zhouqu in Gansu province, which is in the Gannan Tibetan Autonomous Prefecture, according to the official Xinhua News Agency.

A torrential overnight rainfall flooded the nearby Bailong River, which became blocked with mud and debris, creating a 3-kilometre-long lake. The lake then overflowed, sending mud and rocks gushing into the town, smashing cars and toppling buildings. Part of the town was submerged under as much as one metre of water.

CTV's Beijing Bureau Chief Ben O'Hara-Byrne reported Sunday that rescue crews are hampered by both the town's remote location and the amount of mud and water covering the area.

"They're having a very hard time getting heavy equipment into the area that was hit by the mudslide overnight, mainly because of the amount of mud that's still there and the water that came behind it," O'Hara-Byrne told CTV News Channel in a telephone interview. "So roughly 2,800 soldiers are already in the area trying to clear things away."

O'Hara-Byrne said given that power and communications systems have been cut in the area, it is unclear how many of the missing residents are in danger and how many simply cannot be contacted.

"The big concern here is a lot of smaller buildings were ripped right off their foundations as this mud swept through," he said. "And there's concern, especially given the time of night -- that it happened at midnight -- that a lot of people were asleep, that a lot of people were in their homes, that maybe the rain and especially the sound of the flooding itself may not have been enough to wake people up and they wouldn't have had time to get out and get to higher ground."

Explosive experts flown to the scene by helicopter blasted dynamite in the river Sunday to ease the debris and allow for the release of water that could have built up and worsened the flooding.

But the mud and water, as well as narrow access roads, prevented heavy equipment from being brought into the area. In addition to the soldiers working with shovels, picks and buckets to clear the area, more than 1,000 firefighters are being sent to the region to aid in relief efforts. Chinese Premier Wen Jiabao is also on his way to the area.

In total this year, flooding has killed more than 1,100 people across China. More than 600 people are also unaccounted for and more than 9.6 million have been forced from their homes.

With files from The Associated Press