The tests were carried out following the deaths of tens of thousands fish in Angthong and Ayutthaya last Sunday.

The cause could be either a sugar vessel that sank earlier this month or a factory discharging wastewater into the river. While authorities leaned towards the former, local people believed it was the latter.

Natural Resources and Environment Minister Kasem Sanidwong said the test results should be ready next week but they would have to wait until then as they will be used as evidence to establish who the polluter was before seeking compensation for those affected.

Kasem said most of the polluted water had now reached Bang Pa-in.

Head of the PCD's water quality management bureau, Anuphan Ittharatana, said the department would report to the Cabinet on Tuesday about the water pollution in Angthong.

Also on the agenda will be assistance and water rehabilitation as well as compensation payments.

Anuphan also revealed that the initial test result on the water sample found near a monosodium glutamate factory in Pa Moke district found concentrated molasses, a raw ingredient in MSG production.

An inspection of the factory's underground drainage system, which found two pipes going into the river, was put on hold yesterday afternoon. Angthong deputy governor Sumeth Saengnimnuan reportedly told local people it was because it had been determined that the most likely cause was the sugar barge accident.

However, another report said it was to make way for an inspection by wastewater management experts and engineers.

Halting the inspection has upset people but there have been no outbreaks of violence.

Suthep Kakaew, president of the  Bang Sadet Tambon Administration Organisation, said the provincial authority had ended the inspection too soon, despite an agreement on Thursday that

the digging to check the underground pipes would continue until everyone was convinced the factory was not the cause of the pollution.