Updated 15 12.10pm

Two explosions were reported otoday at the flood-hit Arkema SA chemical plant in Crosby, Texas, and a sheriff's deputy was taken to a hospital after inhaling chemicals, the company said.

The company said it was notified at approximately 2 am, by the Harris County Emergency Operations Center of two explosions and black smoke coming from the plant in Crosby.

"Organic peroxides are extremely flammable and, as agreed with public officials, the best course of action is to let the fire burn itself out," the company said.

"We want local residents to be aware that product is stored in multiple locations on the site, and a threat of additional explosion remains. Please do not return to the area within the evacuation zone."

The Harris County Sheriff's Office said on its Twitter feed the deputy had been taken to the hospital and nine others drove themselves to the hospital as a precaution.

The company evacuated remaining workers at the damaged plant on Tuesday, and Harris County ordered the evacuation of residents within a 2.4-km radius of the plant, which makes organic peroxides used in the production of plastic resins, polystyrene, paints and other products.

The Federal Aviation Administration has temporarily barred flights near the plant because of the risk of fire or explosion.

In the meantime, a Reuters analysis of satellite imagery and property data shows that at least $23 billion worth of property has been affected by flooding from Hurricane Harvey just in parts of Texas' Harris and Galveston counties.

The number represents market value, not storm damage, and is but a small fraction of the storm's reach, as satellite images of the flooding are incomplete. Satellite imagery compiled by researchers at the University of Colorado shows flooding across 600 square kilometers of Harris County and 132 sq km of Galveston County, about one-eighth of each county's land area.