"The water is expected to keep swelling," the commission said in a news release on Monday.

One of the country's seven major waterways, the Huaihe drops 178 meters over 360 kilometers in its upper reaches. In its middle reach of 490 km, mostly in Anhui province, however, the drop is just 16 meters, making it difficult for floods to recede in the province. It also passes through Henan, Jiangsu and Shandong provinces.

On Monday morning, the commission issued a red alert for flooding, the highest in a four-tier color-coded warning system, while upgrading the emergency response to Level I, its highest, amid a "grim flood control situation".