More than 5,000 tons of highly toxic industrial waste were dumped illegally in rural areas near a Southwest China city, causing livestock deaths and soil and water pollution, local authorities said over the weekend.

A pond in Qujing, Yunnan province, which was heavily contaminated by illegally dumped toxic industrial waste. [China Daily]?

Water resources experts arrived on Sunday to assess the condition of the Nanpan River, which is the source of the Pearl River, Quan Ende, deputy head of the publicity department in Qujing city of Yunnan province, said on Sunday.

Two truck drivers illegally dumped 5,222 tons of chromium compound waste, a highly toxic heavy metal, in three townships in Qujing city between the end of April and June, the city's publicity department said in a statement on Saturday.

The drivers, identified as local residents Wu Xinghuai and Liu Xingshui, were under contract with Yunnan Province Luliang Chemical Industry Co Ltd, a local chromium producer, to ship the waste to a treatment plant in neighboring Guizhou province, according to the statement.

But the men never made the delivery; instead, they dumped the waste and saved the transport costs, local authorities said.

Both have been placed under arrest.

"Production has been halted at the plant," said a company executive surnamed Pan. "I don't know when it will resume."

Pan added that the company had to take responsibility for the pollution because of its failure to supervise the drivers.

The problem came to the attention of local authorities on June 12, when villagers reported that goats grazing near the dumping sites had died.

The authorities found later that the goats had been killed by drinking water polluted by the chemical waste.

The statement said 77 livestock died from the pollution, with water in a pond and a small reservoir near the dumping sites heavily contaminated with chromium compounds, according to the statement.

However, local authorities said that the pollution had not caused any human deaths or injuries because the source of drinking water for local villagers was far away from the dumping sites.

Water quality in the parts of the Nanpan River that pass through the city wasn't affected, the authorities added.

As of June 17, local authorities had completed the clean-up work for the chromium compound waste and polluted soil, which amounted to 9,130 tons.

In addition, the polluted water, estimated at about 100 cubic meters in the pond, had been recovered and treated at the chromium producer.

The water in the small reservoir, which was less polluted and estimated at about 40,000 cubic meters, had been treated to be safe for animals and human beings, said the authorities.

They also collected and treated about 3,000 cubic meters of polluted water that had leaked from the dumping sites. The combined 43,000 cubic meters of treated water had been discharged into the Nanpan River, they added.

Local authorities were continuing to monitor soil pollution in these areas.

The local government will assess the economic impact of the pollution and compensate local villagers for direct losses within three days, said Quan.

Environmental protection authorities in South China's Guangdong province said on Saturday that no chromium pollution had been detected in the Pearl River, a water source for tens of millions of the province's residents.

The remarks came after posts on weibo.com, a popular Chinese micro-blogging site, claimed that 300,000 cubic meters of chromium-polluted water were piped into the Nanpan River, spawning public concerns over water safety in the country's most populous region.