As many as 100 people were hospitalised after a massive gas leak in Karachi on Friday.

Three people were said to be critical after the leak at Engro Polymer & Chemicals Plant in Port Qasim area, which came only weeks after soybean toxic gas tragedy which had claimed a dozen lives and seriously affected 400 others.

Of the fresh case affectees, at least 19 people were hospitalised at the Pakistan Steel Mills Hospital and 36 were taken to Jinnah Postgraduate Medical Centre.

JPMC Executive Director Dr Seemin Jamali said that 70 patients had been brought to the facility, at least one of whom was in critical condition.

“Around 55 patients were discharged after being provided first aid. Around 15 patients are still at the facility,” she said, adding that all those affected by the incident were facing breathing difficulties. “Some had also complained of a burning sensation in their eyes,” she said.

Engro, in an official statement, said the incident was caused due to the “release of chlorine gas through the vents”.

The issue was quickly addressed and the affectees were immediately taken for first aid to nearby medical facilities, it said. All employees exposed to the gas were being screened.

"Patients were being released once cleared after necessary inspection and necessary first aid. No fainting spells, injuries or fatalities have been reported thus far.”

Engro rejected the reports that the leak was caused due to a boiler explosion. It also said that certain areas of the plant have been taken offline as a precautionary measure. Further investigation to determine the exact cause of the incident ware underway.

The Sindh Environmental Protection Agency (Sepa) later stated that all operations at the factory have been suspended until further notice, while a team headed by the director-general was present at the site of the incident.

Last month, at least a dozen people were killed and over 400 people hospitalised after inhaling toxic gas that was linked to a soybean ship docked at Port Qasim.