Mainland villagers living along the East River - the territory's main source of drinking water - were seen yesterday turning the river into a smelly dumping ground. Concern over the quality of water pumped to Hong Kong rose after officials admitted to the Legislative Council on Thursday that water from the East River was becoming increasingly affected by untreated water discharged from nearby farms and factories. Dr Vincent Chen Rongjun of the Institute of Ecology at the South China Agricultural University, Guangzhou, said farming was a big source of pollution. One pig farm at Niushibu village, Henggang city, churned out a quarter of the river's organic pollutants. Some farms in the Longgang county, and townships of Dongguan, were operating without permits. He said smaller businesses such as tanneries bordering the river also spewed out dangerous chemicals. 'Mercury, cadmium, chromium, copper, arsenic, lead, sulphide, amino nitrogen and phosphates - the list of pollutants in the Dongjiang river is alarming,' he said. Yesterday, in Buji, Shenzhen, untreated water from a nearby factory was being pumped into a tributary of the East River, and workers were seen dumping foam boxes into the river. And at another tributary flowing into the Shenzhen Reservoir, where water is pumped to Hong Kong, villagers were seen digging the river bed for mud to build small embankments. One villager, He Chunyuan, said: 'The water will be purified before being piped to households. I do not think our minor work will do much harm.' Shenzhen director of environmental protection, Zeng Chun, admitted some uneducated farmers had made the river dirty. Mr Zeng hoped new laws recently endorsed, under which polluters could face a maximum of seven years' jail, would help prevent pollution along the East River.