HOUSTON (Reuters) - The operators of a Crosby, Texas, chemical factory that ran out of electricity needed to keep flammable material refrigerated will burn the remaining trailers holding the substance, officials said on Sunday.

FILE PHOTO: The flooded plant of French chemical maker Arkema SA, which produces organic peroxides, is seen after fires were reported at the facilty after Tropical Storm Harvey passed in Crosby, Texas, U.S. August 31, 2017. REUTERS/Adrees Latif/File Photo

Arkema SA, the French chemicals company that runs the plant, and Harris County fire officials decided to burn the 6 remaining trailers of organic peroxides, each storing about 500,000 pounds of the materials as a “proactive measure.” Three trailers already caught fire and burned.

The 46-year-old plant lost power after becoming flooded by Tropical Storm Harvey. Staff tending to the materials, which are extremely flammable if not kept at low temperatures, loaded containers of the chemicals into trailers and activated backup cooling systems. They evacuated after additional safety systems and backup generators failed.

The U.S. Chemical Safety Board last week said it has begun an investigation into the fires at the plant, which is about 25 miles (40 km) northeast of Houston.

Arkema, fire and Texas environmental officials said in a statement the fires do not pose what it called additional risk to the area.

An Arkema spokeswoman did not immediately reply to questions on how the company plans to ignite the chemicals. The Harris County Fire Marshal’s office did not immediately respond to requests for comment.

County officials last week evacuated residents and installed a 1.5 mile perimeter around the area, and warned the materials would likely catch fire as temperatures in the trailers rose. The chemicals are used as catalysts in the manufacture of plastic resins, polystyrene paints and other materials.

Texas Environmental officials and the EPA said in a statement on Sunday that “rather than risk additional damage to the facility or spreading (fire) into the surrounding area,” local fire officials would start a controlled burn rather than wait for the containers to ignite on their own.

Air and water monitoring in the area is underway, they said. No toxic concentration levels have been found in areas away from the plant, the statement said.

The EPA sent aircraft to test the smoke from the fires. Officials on Sunday advised people to stay out of the area, avoid smoke and flood waters.