NEW DELHI — A gas leak at an LG Corp. chemical plant in the port city of Visakhapatnam in southern India left 11 people dead and more than 340 hospitalized early Thursday, according to federal and local authorities.

The factory manufactures polymers used to make plastics for LG, a South Korean multinational company best known for its consumer durable products.

The plant had been shut since mid-March, when India implemented a strict nationwide lockdown, and was expected to restart operations this week as the country begins to lift restrictions.

Around 2:30 a.m. Thursday, a thick fog shrouded the area near the factory, on the outskirts of the city, according to witnesses who say they woke up short of breath. Officials say the gas spread throughout a two-mile radius.

“We were sleeping at the time. Suddenly, we felt suffocated from an unfamiliar gas smell,” said 36-year-old Addala Lalitha Kumari, who lives close to the plant. “One of my daughters was gasping.”

Images from local media showed people collapsing on streets. Policemen fanned those lying unconscious on the pavement. Parents rushed crying children into ambulances. Carcasses of dead animals lay in the streets. Many of those hospitalized complained of nausea, vomiting and breathlessness.

Two of the dead were children under the age of 10.

Srijana Gummalla, commissioner of the Greater Visakhapatnam Municipal Corporation, said the gas leaked was styrene, used in the production of plastics. Officials said that the gas was “toxic” and “injurious” to human health but that those who survived were unlikely to face long-term health issues.

“The preliminary understanding is that the leakage is from a valve not handled well by a worker,” Gummalla said.

A spokesman for LG Chem, the affiliate that owns the plant, in South Korea did not immediately respond to a request for comment.

The Reuters news agency reported the company released a statement saying it was “assessing the extent of the damage on residents in the town and are taking all necessary measures to protect residents and employees in collaboration with related organizations.”

According to the U.S. Environmental Protection Agency, short-term exposure to styrene can cause irritation in the eyes, affect mucous membranes and have gastrointestinal effects.

About 1,500 families living in the vicinity of the plant have been evacuated. Residents were advised to cover their noses and mouths with wet masks and stay indoors.

Kumari said her family ran when a relative banged on their door. Outside, she said, there was mayhem.

“People had fainted on roads and were struggling to breathe,” she said. “I didn’t even know if they were dead or alive.” 

Fire engines doused the area with water to mitigate the impact of the gas. Officials said that while the spread had largely been controlled, a strong smell remained and could take up to eight hours to subside.

In a second episode on the same day, seven workers at a paper mill were hospitalized in the central state of Chhattisgarh after a reported gas leak, according to news agency ANI.

India was the site of the world’s worst industrial disaster in 1984 in the city of Bhopal, when a gas leak in a pesticide factory left thousands dead and hundreds of thousands injured.

B. Kartheek in Suryapet, India, contributed to this report.