CHENNAI: A minor ammonia leak was reported at the United Breweries plant in Aranvoyal near Tiruvallur on Saturday after a valve released a small quantity of gas during maintenance work, officials said.

The incident which comes just over a month after a major ammonia leak at St Peter & Paul Sea Foods Exports in Kannigaipair near Periyapalayam in the same district, where a refrigeration system leak claimed 18 lives and left dozens hospitalised triggered panic in the neighbourhood.

According to the Tiruvallur Revenue Divisional Officer (RDO), the incident occurred while a valve connected to the ammonia system was being replaced and tested. A small quantity of gas escaped during the process, triggering the plant's safety alarm system as a precaution.

"The alarm went off when a small amount of gas escaped during the valve change. A few workers stepped out after hearing the alarm, but no one was affected," the RDO said. He dismissed reports that several workers had fallen ill, adding that such valve testing forms part of routine maintenance.

Following the incident, ambulances arrived at the spot, causing concern among the residents. Officials from the Directorate of Industrial Safety and Health (DISH), Tamil Nadu Pollution Control Board (TNPCB), Revenue Department and Sevvaipet police inspected the plant.

Kavitha, Joint Director of DISH, Tiruvallur, who inspected the facility, said: "It was only a slight leakage from a small valve. The factory contained it immediately. No one was affected, and there were no injuries or cases of workers fainting."

In a statement, United Breweries Limited said the leak was detected promptly by its team and operations resumed shortly afterwards. The company added that the cause of the incident was being investigated in line with standard procedures.