An iconic lake at the heart of a popular beauty spot in the southwestern Chinese province of Yunnan has turned milky-white with pollution from nearby companies, local residents and officials said.
Local residents began posting photos online in recent days of the now turbid and white waters of Erhai Lake in the tourist region of Dali, historically famed for its crystal-clear waters.
The reports on social media sparked an investigation by the Dali prefectural environmental protection department, the government said in a tweet on its official microblog account.
"Regarding the problems highlighted by netizens, the Dali prefectural environmental investigation team tested [the waters]," it said.
"The Dali municipal government must now complete clean-up measures within the next 10 days, and pursue and punish those enterprises suspected of causing the pollution according to law," said the statement, posted on Monday.
It blamed "unauthorized waste outlets" for the rise in pollution levels, calling for measures to be taken against "private and unauthorized sewage pipes installed by individuals and organizations."
One Dali resident, however, said there were few companies on the lake, but the government had not kept up with a rapid rise in waste produced in the area.
Local residents blamed the pollution on an influx of migrants from elsewhere in China, the resident, Wang Pusheng, said.
"The population of Dali has risen very fast, and there are a lot of migrants from elsewhere," he told RFA's Mandarin Service.
"There basically aren't any enterprises around Erhai Lake, but the government has been very slow to deal with all of the rubbish and wastewater, which has also been on the rise."
He said local residents are keenly aware of the need to protect the environment, in a region that depends mostly on tourism for its economic growth.
"After the pollution, a lot of local residents have been posting photos online and passing them around."
More than three decades of breakneck economic growth have taken their toll on China's natural resources, sparking a huge increase in public unrest linked to environmental degradation and health problems caused by pollution.
But activists who confront the authorities and vested commercial interests over pollution say they are often subject to revenge attacks and government harassment.
Wu Lihong, an environmental activist who served a jail term for campaigning against pollution on Taihu Lake in the eastern province of Jiangsu, said there are many parallels between Erhai and Taihu.
"Taihu Lake is the same as Erhai Lake. It was once a crystal-clear lake, but now it is very severely polluted," Wu said.
"It's impossible to shut down the chemical plants along its shores," he said. "Some of them relocated to northern Jiangsu, where they are polluting the soil and water there, instead."
Wu said the problem lies with collusion between local government officials and polluting enterprises.
"Why do local officials invite polluting industries in? They have shares in these polluting enterprises, so they are hoping to make a packet out of them," he said.
"The government and the companies are all in it together."
Welcoming polluting industries
He said governments in the poorer rural regions of China's west are usually happy to welcome polluting industries shunned by residents of richer coastal cities in the east of China.
"They don't take environmental pollution seriously, in spite of a whole raft of rules and laws issued by the central government," Wu said.
"When it comes to policy, where there's a will, there's a won't."
Officials have admitted that China is facing a "grave" environmental crisis, with more than half its cities affected by acid rain and one-sixth of its major rivers too polluted to use for watering crops.
But activists say cleaning up China's highly polluted lakes and rivers could take far longer than the three decades it took to foul them up in the first place.
Reported by Gao Shan for RFA's Mandarin Service. Translated and written in English by Luisetta Mudie.