More than 300 homes in the Tampa Bay area have been ordered to be evacuated.
Emergency crews in Florida have been working to prevent a “catastrophic” flood after a leak was found in a large reservoir of toxic wastewater.
More than 300 homes near Tampa Bay have been evacuated, and a highway near the Piney Point reservoir has been closed.
Florida Governor Ron DeSantis declared a state of emergency on Saturday.
On Sunday, he said the water was “primarily saltwater” from a dredging project mixed with “legacy process water and storm water runoff”.
He added that the water was not radioactive, as had been feared, and that the priority was to prevent a “real catastrophic flood situation”.
Officials said the 77-acre (31-hectare) reservoir holds millions of gallons of water containing phosphorus and nitrogen from an old phosphate plant.
The pond where the leak was found is in a stack of phosphogypsum, a radioactive waste product from the manufacture of fertiliser.
Attempts to repair the leak late on Friday, by plugging the hole with rocks and other materials, were unsuccessful.
Declaring a state of emergency allowed funds to be released to send more pumps and cranes to the area.
On Sunday, Mr DeSantis said emergency workers – assisted by the Florida National Guard – were pumping water out of the pond at a rate of 33 million gallons a day.
Other workers have been charting the path to control the flow of the water.
Manatee County Administrator Scott Hopes told a press conference on Saturday that there were concerns the water could flood the area, which is mostly agricultural.
“We are talking about the potential of about 600 million gallons (2.3 billion litres) within a matter of seconds and minutes, leaving that retention pool and going around the surrounding area,” he said.
By Sunday, however, he was more optimistic – telling reporters that the situation should be in a “much better position” by Tuesday.
But he also warned that “we are not out of the critical area yet”.
National conservation group the Center for Biological Diversity also released a statement calling for the US Environmental Protection Agency to intervene.
“Federal officials need to clean up this mess the fertiliser industry has dumped on Florida communities and immediately halt further phosphogypsum production,” Jaclyn Lopez, the organisation’s Florida director, said.