HANGZHOU -- Five people have been detained on suspicion of dumping 300 tonnes of diseased pigs in a mountainous area of Huzhou city, eastern China's Zhejiang province.

The city government issued a circular Monday accusing the Huzhou Industrial and Medical Waste Treatment Company of sending pigs that died of disease to a landfill rather than for cremation between 2013 and 2014.

Police investigation shows that the company, which is responsible for disposing the city's dead pigs, has a refrigerated storage facility with a capacity of 50 tonnes. For six times, the company dumped diseased carcasses at three sites at Dayin Mountain whenever the facility was full.

Over the last week, the Huzhou government had dug out 224 tonnes of decomposed carcasses and sludge, which will be cremated.

A sample-test report by the municipal agricultural department said that no human-infecting pig diseases, such as H5 and H7 bird flu viruses and foot-and-mouth disease, had been found.

The authorities have ordered that the public security bureau, agriculture and environmental department and the local government to collectively ensure no carcasses are left in the soil. Later, local environmental service center will carry out an environment impact assessment.

The Zhejiang provincial government has sent inspectors to oversee the treatment process.

East China provinces are known for breeding pigs, and there are rules for disposing of carcasses. However, illegal dumping occasionally occurs when dealers try to save on bio-safety costs.