Workers were still reinforcing the collapsed area with stones on Thursday evening and the breach was expected to be completely closed on Friday, according to the provincial flood control and drought relief headquarters.

Chen Wenjun, vice director of the headquarters, said an increasing area of the cropland at the lower reaches was being flooded.

Yet he fuled out the possibility of a large-scale flood because "the whole situation is already under control".

The two-kilometer embankment, which narrows the watercourse of the Yellow River, collapsed at 4:10 p.m. on Tuesday after floodwater cascaded downstream in Dali County, said the headquarters.

It said the collapse was caused by a flood peak formed last Friday upstream, which came barreling down the river at 3,710 cubic meters per second.

About 400 farmers who were harvesting cotton and corn in the adjacent area were evacuated after the collapse.

No casualties have been reported. More than 600 hectares of cropland were inundated.

The flooding had destroyed at least 200 ha cropland, the sources said.