What police initially called a chemical spill in Fort Pierce prompted evacuation for a time Thursday.
It happened Helena Chemical Company at 3630 Selvitz Road and police said officers evacuated an area for a half mile in each direction.
Brenda Stokes at St. Lucie County Fire Rescue said a liquid fertilizer mix in a tank overheated and a chemical was released into the air. It was possibly the result of a faulty valve.
Workers poured cold water over the tank and were able to cool it down.
She said the release happened in an industrial area and there were no homes in the immediate vicinity.
Police closed Selvitz Road from Edwards Rd south to Midway Road for a time.
There were no initial reports of injuries.