Dead pigs are seen drifting after a farm flooded by heavy rainstorms in Liuye Township in Southwest China's Guangxi Zhuang Autonomous Region on June 16, 2015. [Photo/Xinhua]

NANNING -- A total of 16,000 pigs drowned at a farm flooded by heavy rainstorms in Southwest China, leaving authorities with the challenging task of sterilizing the carcasses.

The flooding occurred on Sunday morning. According to Wang Lin, the manager of the pig farm, it happened too fast for them to evacuate the pigs.

The pig farm was located in Liuye Township in Southwest China's Guangxi Zhuang Autonomous Region, where precipitation in the last 20 hours has reached 390 mm, with rain battering the region since last week.

Thousands of carcasses were floating in the floodwaters. Pigs that managed to survive the flooding were seen crawling to the shore or climbing on rooftops. Some of the dead pigs have begun to rot and are emanating a foul smell detectable from hundreds of meters away.

Such a large number of animals drowning in a single event is unprecedented in the autonomous region, said Nong Yingxiang, an official with the autonomous region's animal health watchdog.

Local authorities have set up a team to bury and sterilize the swine. A burial spot has been selected and the carcasses still in the river will be salvaged by Wednesday. The clean-up is expected to finish in seven days.

Though the pigs died from natural disasters, limiting the risks of spreading epidemics, Nong cautioned that carcasses can rot faster at high temperature and will pollute rivers and cause infectious disease if not immediately cleaned up.

Heavy rains have lashed much of south China over the past few weeks, causing floods and landslides, bringing down buildings and killing crops in the region. The latest rainstorms in the autonomous region have killed eight people so far and left three others missing, local authorities said Tuesday

In March 2013, thousands of dead pigs were seen drifting in Shanghai's Huangpu River at the lower reaches of the Yangtze River, causing public concern over the contamination of water sources for the city.