BEIJING (AFP) - At least 170 dead pigs have been found in a Chinese river, state media reported on Thursday - the latest in a string of similar incidents that have raised fears over food safety.

The animals were found floating in a tributary of China's second-longest waterway, the Yellow River, in north-western Qinghai province, the official Xinhua news agency said.

The grim discovery follows a series of scandals involving dead pigs in Chinese rivers. Last year 16,000 carcasses were found drifting through the main waterway of the commercial hub of Shanghai.

In Qinghai - the furthest west such an incident has been reported - "the source of the dead pigs is still under investigation", Xinhua said, citing the local authorities.

Industry analysts say sick pigs are sometimes dumped in rivers by farmers hoping to avoid paying the costs of disposing of the animals by other means.

Around 500 dead pigs are recovered every month from a Chinese reservoir in the south-western province of Sichuan, the state-run media reported in March.

The authorities also found 157 dead pigs last month in a river in central Jiangxi province.

China is a major producer of pork, which surveys have found to be the country's most popular meat.