After the dike breach, an embankment considered the second line of defense was threatened on Monday.

The embankment, about 2 kilometers from the breached dike and 14.3 km long, separates Tuanzhou from the nearby township of Qiannan.

Multiple piping hazards — the movement of water through channels in the embankment — were observed, but they have been brought under control, local authorities said on Monday.

More than 300 police officers and firefighters have been working at the site to deal with the piping effect.

Zhu Dongtie, head of Hunan's Department of Water Resources, said the embankment has not been used to prevent flooding since 1996, and it was built to a much lower standard than the dike.

Twenty-four incidents of leakage and piping at the embankment have been dealt with, he said.

Despite all the difficulties and challenges, the embankment must be safeguarded, he added.

The dike breach followed 17 days of heavy rainfall in Hunan, the longest continuous period of heavy rain since 1961.