Authorities are reportedly probing a pig farm in central China for dissolving dead pigs in a chemical solution and pumping the resulting remains down its drains, which empty into a river.

Huasheng Online, a news website published by the Hunan Daily Press Group, said environmental protection and animal hygiene authorities in Changsha, Hunan province, were investigating the allegations.

The farm claimed that using strong alkali to break down carcasses before flushing them away was a non-harmful method of disposal for pigs that died of disease, the report said.

But users of China's Twitter-like microblogs were disgusted. "It's absolutely illegal and absolutely harmful," wrote one using the name Quxiaolijie.

"The only non-harmful way to dispose of dead pigs is to burn them or bury them. They absolutely can't be discharged into the river. Strictly investigate and strictly punish!"

Food safety is a major issue in China following a string of scandals, including the discovery in March of thousands of dead pigs floating down a Shanghai river.

No official explanation has been provided for the incident, which lasted for several days and was a major embarrassment for China's commercial hub.

Last month the public security ministry announced that 900 people had been detained for meat-related crimes including selling rat and fox meat as beef and mutton.

In another recent incident, US fast food giant KFC was hit by controversy after revealing some Chinese suppliers provided chicken with high levels of antibiotics, in what appeared to be an industry-wide practice.