An embankment seen as the second line of defence following a dyke breach in Hunan province was under threat on Monday, local authorities said.

More than 300 police officers and firefighters were working at the site to stem the piping effect that is eroding the embankment in Huarong County, said the province's water resources department.

The 14.3km embankment is located around 2km behind the dyke that burst on Friday at Dongting Lake, China's second-largest freshwater lake, following a heavy rainstorm.

The piping effect can hollow out a dyke and lead to a burst if not properly handled.

At least 7,000 residents have been evacuated following the dyke burst on Friday, and workers have been racing against time to seal the 226m breach. (Xinhua)