The fight to drain a dangerous debris-formed lake gained new urgency Wednesday amid fears that a breach could bring further devastation to a northwest China county that was leveled by the country's deadliest mudslide in decades on Sunday.

The weather bureau warned Wednesday of heavy rains and more potential geological disasters in the next five days on the upper reaches of the Bailong River, above Zhouqu County, in Gannan Tibetan Autonomous Prefecture of Gansu Province.

The rains could cause the unstable lake on the Bailong River to burst and flood the already-devastated areas where people are still hunting for survivors.

The provincial government has ordered a mass evacuation of residents in areas prone to flooding and geological disasters.

By 8 a.m., the water level of the lake was down by 80 cm from the highest level reported after the mudslide swept through the county on Sunday, the emergency rescue headquarters said in a press release.

Meanwhile, it said, the lake's water volume had been halved from 1.5 million cubic meters to 700,000 cubic meters.