The operators of a flooded chemical plant outside Houston warned Wednesday they are dealing with a "critical issue" as a result of Harvey's torrential rains and have no means to prevent a possible explosion at the site.

As a precautionary measure officials had already ordered the evacuation of an area within 1.5 miles (three km) of the organic peroxides plant in Harris County, which is owned by French group Arkema.

Rich Rowe, president and chief executive of Arkema Inc, said in a statement that the facility in the town of Crosby had been evacuated for employees' own safety following a dangerous loss of on-site refrigeration.

"Right now, we have an unprecedented six feet of water at the plant," Rowe said. "We have lost primary power and two sources of emergency backup power."

"As a result, we have lost critical refrigeration of the materials on site that could now explode and cause a subsequent intense fire," he added.

"The high water and lack of power leave us with no way to prevent it."