Pollution in The Chao Phya River, which killed tens of thousands of fish on Sunday night in Angthong and Ayutthaya, reached Greater Bangkok yesterday with the authorities urging people not to use it.

Royal Irrigation Department (RID) spokesman Boonsanong Suchatpong yesterday said the situation was "getting back to normal" in Angthong, Ayutthaya and Pathum Thani, where dissolved oxygen (DO) levels in the water were now above three milligrams per litre, which would enabled river life to survive.

When the polluted water from Angthong reached Ayutthaya on Tuesday, the governor declared Bang Ban, Bang Pa-in, Phra Nakhon, Si Ayutthaya and Bang Sai districts "disaster zones".

The contaminated water arrived in Nonthaburi yesterday afternoon - causing the DO levels in the Pak Kred district to drop to 2.93 mg/l - and reached Bangkok last night.

By then the water had been heavily diluted as the RID released more water from Pasak Cholasit and Rama VI dams at 90 cubic metres per second, said Boonsanong, who urged city residents to use tap water instead of river water.

Metropolitan Waterworks Authority (MWA) governor Vithit Avuchanont said the MWA received calls from worried city residents and wanted to confirm that the low DO levels in the Chao Phya would not affect the MWA's capacity to produce clean tap water.

The water at the Pathum Thani's Sam Lae pumping station was of "good quality" with DO levels of 4.5 mg/l to 4.7 mg/l, he said. As precaution, the MWA has temporarily closed the sluice gates and could still use water in the MWA channels to meet people's needs, he added.

Angthong governor Wiboon Sanguanphong met Ayutthaya governor Cherdphan na Songkhla, other officials and farming

representatives yesterday to discuss ways to determine the source of the pollution.

It is believed to have come from either a factory or from a boat carrying sugar that sank over a week ago.

The meeting gave less weight to the sunken boat carrying 650 tonnes of sugar because the sugar was removed after the accident and what little remained would have been insufficient to cause the contamination.

Angthong governor Wiboon said fish farmers would receive compensation of Bt257 per square metre - up to 80 square metres per case - in accordance with the Fisheries Department regulations.

The province will also help them file criminal and civil lawsuits against the offender and Angthong attorney Apichat Thananchaya has prepared pro-bono lawyers for the affected farmers, the governor said.

Boonrod Pramuansukhom, 47, who was among the 100 farmers at the meeting, said no clear conclusions had been drawn and if it remained unsolved, villagers would go to Bangkok to "request justice" from the Prime Minister.

The fish farmer said he believed a monosodium glutamate factory belonging to KTMSG in Pa Moke district, where farmers dumped dead fish during a rally on Tuesday, was the suspected culprit and urged the authorities to inspect the plant's wastewater system.

However, KTMSG executive Wichai Sutthilertworakul denied the allegation, claiming the factory never discharged contaminated water into the river.

He said pipes linked to the river were to pump water in for the factory's use - and not to discharge wastewater into the river as alleged.

The protest at the factory turned ugly last night when demonstrators blocked the entrance preventing a deputy governor, members of the media and some senior civil servants visiting the plant, from leaving.

Farmers were demanding the temporary closure of the factory pending the pollution investigation's results and insisted that Angthong's governor sign the closure order in front of them, before they would agree to disperse.

Wiboon could not be reached for a comment when The Nation went to press.

Chulalongkorn University's Faculty of Veterinary Science deputy dean Jennuch Wongtawatchai said an initial test found that the massive loss of fish did not come from an infection.