The Phra Prong River in Prachin Buri was clean until eight years ago, when residents say factories began to pollute the water, killing huge numbers of fish.

A villager shows some dead fish collected from the Phra Prong River.

Ratana Sriwarakul, a member of a Phra Prong River Basin Network, said local communities have been using chemicals in agriculture for decades.

But villagers had never experienced such large fish kills _ an event that now occurs two or three times a year.

The network comprises representatives from 15 tambons in eastern Sa Kaeo and Prachin Buri.

The group once found evidence of a starch-making company polluting the water.

But even though the network won a court case and was awarded 1 million baht in compensation, the company has appealed.

To date, no other factory in the area has been caught in claims of causing pollution.

The Industrial Works Department said there are seven factories in the river basin.

They belong to Thai Cane Paper Plc, Elite Craft Paper Co, Ruey Tay Fibre Industry (Thailand) Co, Srakaew Charoen Co, Thai Ping Ethanol Co, Thai J Press Co and Charoen Pokphand Foods Plc.

The department signed a memorandum of understanding (MoU) with the seven factories and the communities this month to protect the area from further damage from pollution. The MoU lets communities visit the factories once a month.

Deputy director-general Pongtheb Jaru-ampornparn blamed the farm sector for the wastewater, saying the factories were closed for holidays and maintenance when the pollution events occurred.

Water quality improved following tests.

"The best method is to stop pointing fingers at each other and perform tests right away when something happens," said Mr Pongtheb.

Mrs Ratana insists the agriculture sector cannot be polluting the water on such a large scale, and other agricultural areas in Prachin Buri have not experienced the same problems.

"As far as I can tell, signing the MoU has been of no use," she said.

"There is collaboration in making this sort of event happen, and when money is involved you can always get people to come but without honesty. When they leave, they are on their own."

Mrs Ratana said everyone should play a role in monitoring the water situation when factories announce the time frame for releasing water.

Many times evidence gathered by the communities has not been admissible in court, as it was not prepared by professionals, she said.

Thus, the factories can usually get away with what they are doing.

Prapas Ruksri, head of the Bo Thong Tambon Administration Organisation, believes the pollution is caused by the industrial sector and said it often comes during long holidays for government officials.

"During these periods, industries have an opportunity to release wastewater, as there are no government officials available for us to contact," he said.

"The factories intend to release water during these long holidays. What we want is to develop the Phra Prong into an area of tourism and organic agriculture. If the water quality is good, then it can be used for farming year-round."