At least 70 people were affected by a gas leak at Engro Polymer & Chemicals Plant in Karachi's Bin Qasim area, officials said on Friday.

According to an official statement from Engro, a copy of which is available with Dawn.com, the incident was caused due to the "release of chlorine gas through the vents".

The statement said: "The matter was quickly contained and the affectees were immediately taken for necessary first aid to nearby medical facilities. Patients were being released once cleared after necessary inspection and necessary first aid. No fainting spells, injuries or fatalities have been reported thus far."

The press release said that due to the incident, specific areas of the plant have been "taken offline" as a precautionary measure, adding that further investigations to ascertain the exact cause of the incident are under way.

The statement also clarified that the incident did not occur due to a boiler explosion, adding that all employees exposed to the gas were being screened.

However, Jinnah Post Graduate Medical Centre (JPMC) Executive Director Dr Seemin Jamali said that 80 patients had been brought to the facility, at least one of whom was in critical condition. She later clarified that 70 people had been brought to the facility.

Speaking to Dawn.com, Jamali maintained that an emergency had been declared at the hospital due to the gas leak.

"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.

Taking notice of the incident, the Sindh Environmental Protection Agency (Sepa) 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.

In a statement, Sepa added that Sindh government spokesperson Murtaza Wahab was overseeing the operation. The press release said that personal hearing notices were also being sent to the company over the incident, while teams were being sent to JPMC and Aga Khan University Hospital to assess the condition of those affected.

According to Malir SSP Mohammad Ali Raza, the incident occurred after a gas pipe burst at the factory.

"The gas leak affected all those that were present in the area," he said, adding that work was under way to repair the broken pipeline.

"The gas supply to the factory has been suspended for now, while all factory workers have been evacuated from the area," he said. He later added that factory workers were allowed back in after the situation was brought under control.

Malir SP Tahir Noorani added that between 30 to 40 people became unconscious due to the gas leak, and had to be hospitalised. "They were later discharged after being provided first aid," he said.