KUNMING - Six workers are missing in Southwest China's Yunnan province after water escaped on Friday from a barrier lake formed by an August earthquake.

At around 3:20 pm on Friday, 20 people were digging tunnels to allow the water to discharge from the lake safely.

"They were about to place dynamite to blow up the blockage, but suddenly water burst through and flooded the construction site," said a Yunnan official on Saturday.

Ten workers escaped, but 10 others were washed away. Four were rescued and are being treated at Qiaojia People's Hospital. More than 300 rescuers are involved in the search.

The lake is 15 km long and covers an area of 49 square km in Qiaojia and Ludian counties. It was formed when landslides blocked the Niulan River.

Hundreds of residents downstream of the lake have been evacuated, given the possibility of the lake completely bursting its banks.

The August quake left over 600 people dead and 112 missing in Yunnan.

Barrier lake poses danger in China quake zone	Yunnan quake lake rising alarmingly