CHENNAI: Four contract workers fell unconscious after inhaling toxic fumes while cleaning a wastewater tank at a private factory near Sriperumbudur in Kancheepuram district on Tuesday. Two of them are currently in the intensive care unit of a corporate hospital in Porur, police said.

The incident took place at United Industries Plastic Private Limited, an automobile spare parts manufacturing unit with over 500 employees, located in Vengadu village near Sriperumbudur.

Authorities said waste from the manufacturing process—including paint residue and chemicals—had accumulated in an underground tank roughly 40 feet deep. The tank was reportedly cleaned only once a year.

According to police, three contract workers entered the tank Tuesday afternoon after it became full. Soon after starting the cleaning, they inhaled toxic fumes and began losing consciousness. Their cries for help prompted six co-workers to rush in for rescue.

Four workers—identified as Manikandan, Madhanraj, Vignesh, and Sridhar—were found affected by gas exposure.

All four were first taken to Sriperumbudur Government Hospital in a '108' ambulance. After conditions of two of them deteriorated, they were moved to a private hospital in Porur for specialized care, where they remain in intensive treatment.

Acting on a hospital alert, a police team from Sriperumbudur police station visited the hospital and recorded statements from the injured workers.

Police have detained company officials and the contractors who hired the workers for the cleaning job for questioning. Further investigation is ongoing.