The death toll have surged to 589 following Sunday's quake in Yunnan Province, including 504 reported in worst-hit Ludian County and 72 in Qiaojia County.
Risks of flooding also loom over a growing barrier lake with a water volume of 49.6 million cubic metres, which has led to evacuation of 4,200 residents living on the lower reaches of the Niulan River, located near the junction of Ludian and Qiaojia.
Sun said that hydrological experts are mulling a scheme to handle the lake.
Located 8.2 km away from the epicentre of Ludian's Longtoushan Township, the lake was formed by a landslide blocking the river.
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The tremor has also left 2,400 injured. Nearly 230,000 people were suffering from acute water and food shortages.
Nine people in Qiaojia were reported missing.
Rescue operations, hampered by downpours and frequent traffic disruptions, are facing acute time pressures as the likelihood of survivors declines after 72 hours.
Two "miracles" have inspired optimism among rescuers as two senior residents, aged 88 and 76, in quake-flattened Babao Village were pulled out of debris about 50 hours after the disaster, state-run Xinhua news agency reported.
Yesterday, health institutions in Zhaotong City, which administers Ludian, had treated 1,947 people, including 43 whose lives were in danger.