"We noticed abnormality on Dec. 26 at 11:30 p.m. local time (1800 GMT) in the ammonia unloading subsea pipeline near shoreside, outside the plant premises," Coromandel said in an exchange filing earlier in the day.
Forty-four people were rushed to Akash Hospital in Chennai, two hospital officials told Reuters, on condition of anonymity, as they were not authorised to talk to the media.
Six others were admitted to Stanley Medical College and Hospital near Ennore, local media reported earlier, quoting Tamil Nadu Health Minister Ma. Subramanian.
The Tamil Nadu government said in a statement that the leak took place when Coromandel's fertiliser manufacturing unit was preparing to receive an ammonia shipment through its 2.5 kilometre-long (1.5 mile) undersea pipeline.
"The unit observed pressure drop in the pipeline at around 11.45 pm and simultaneously observed pungent odour around the storage terminal and near the material gate," the statement read.
"They will identify the exact location and the extent of pipeline damage within a day and will rectify the same before commencing the ammonia transfer."
"All are safe and normalcy is restored. We have informed relevant authorities about the incident," Coromandel added.
Coromandel's shares dropped as much as 3.7% on Wednesday, before closing 1.6% lower.
The incident comes weeks after an oil spill in the same area from a refinery belonging to Indian Oil-owned Chennai Petroleum Corp during Cyclone Michaung.
(Reporting by Nandan Mandayam in Bengaluru and Praveen Paramasivam in Chennai; Editing by Sohini Goswami)
By Praveen Paramasivam and Nandan Mandayam
