A federal lawsuit has been filed by three central Florida residents who live near a fertilizer plant where more than 200 million gallons of contaminated waste water leaked into one of the state's main underground sources of drinking water.

The proposed class-action lawsuit filed Thursday seeks to recover damages, including for the residents' possible losses of private wells, and for water testing, monitoring and treatment.

Mosaic, the world's largest supplier of phosphate, said a sinkhole opened up beneath a pile of waste material called a "gypsum stack." The 215-million gallon storage pond sat atop the waste mineral pile. The company said the sinkhole is about 45 feet in diameter.

Mosaic says it's monitoring groundwater and has found no offsite impacts. It's also offering free drinking water testing to the community.