The Tamil Nadu Pollution Control Board has detected four unauthorised dyeing units that were discharging effluents into River Noyyal through drains, during raids conducted over the last few days. Official sources said of the units, three were located at K. Chettipalayam and Thennampalayam in the Tirupur knitwear cluster and one in the hinterland.

“Two of the units have installed large scale winches that are capable of dyeing almost 500 kg of fabric in a ‘single lot’,” officials said. Of the other units, one was involved in the dyeing of accessories used in the apparels and another in small-scale dyeing of fabrics.