Tamil Nadu Pollution Control Board today sealed 23 dyeing units attached to a common effluent treatment plant in nearby Tirupur, for allegedly polluting Noyyal river, the lifeline of three districts.

Based on the complaint by some villagers that coloured water was being discharged to river from the plant at Kasipalayam and effluents to a 150-acre irrigation tank in Manickapuram village, the board officials monitored the matter.

Though investigations revealed that there was a pipe burst, resulting in the leak to the tank, the villagers succeeded in proving that the effluents were discharged at night.

They claimed that the dyeing units were taking advantage of the monsoon and releasing the effluents so that the colour will be muddy and will get diluted, police said.

The board directed stoppage of production in 23 units until further orders.