WASHINGTON (Reuters) – French chemical firm Arkema SA (AKE.PA) said an evacuation zone put in place amid fears that more flammable organic pesticides at its flooded plant in Crosby, Texas, would explode was lifted on Monday after the materials were ignited in a controlled burn.

The plant, which makes organic peroxides for the production of plastic resins, polystyrene, paints and other products, was swamped by as much as 6 feet (1.83 m) of water due to Hurricane Harvey and had been without electricity since Aug. 27.

Starting on Thursday, three of the nine trailers at the facility containing a total about 500,000 pounds of chemicals exploded and caught fire. The company had warned it expected a series of fires as temperatures in the trailers rose without functioning cooling systems.

In a statement on Monday, Arkema’s North American unit said the 1.5-mile (2.4-km) evacuation zone ordered by Harris County authorities since Tuesday had been lifted. On Sunday, the company said it had safely caused “ignition of the remaining” six containers which had then “largely burned themselves out.”

The U.S. Environmental Protection Agency and the Texas Commission on Environmental Quality said on Sunday fire officials would perform a controlled burn of materials at the facility, located about 25 miles (40 km) northeast of Houston, to avoid further damage and limit the risk to the surrounding area.

The environmental officials said they would continue to monitor air quality around the plant.

The EPA has said its testing methods have not found toxic concentration levels in smoke from the plant in areas away from the evacuated facility since explosions were first reported on Thursday.

The plant lost refrigeration when backup generators were flooded, prompting workers to transfer products from warehouses into diesel-powered refrigerated containers. The company said refrigeration of some back-up containers was compromised because of high water levels.

Last week, 15 Harris County Sheriff’s deputies were briefly taken to a hospital after inhaling smoke from fires at the Arkema plant but were released soon afterward.

The Federal Aviation Administration last week temporarily barred flights near the plant because of the risk of fire or explosions.

The company said it is opening an assistance center at Crosby to provide financial assistance to people who were affected by the evacuation order near the plant.