Ammonia gas leaked from the state-owned Fertilisers and Chemicals Travancore (FACT) plant at Ambalmugal near here late Thursday, causing breathing problems among local residents. The factory said later the leak had been rectified.
FACT officials said the leak was detected around 8 p.m. and was rectified.
However, with the gas escaping into the air the locals found it difficult to breathe.
TV reporters who arrived at the scene told IANS that the area still had a foul smell even after two hours.
The authorities opened a medical camp at a school nearby for those suffering from breathing problems. Everyone in the camp is out of danger, the authorities said.
Most people have begun returning to their homes.