RIVERVIEW – About 40,000 gallons of acidic process water leaked from a pipe at Mosaic Fertilizer plant, causing a small fish kill, according to environmental and company officials.

The leaking pipe, which runs under U.S. 41, was detected about 10:30 p.m. Wednesday, according to Mosaic spokesman David Townsend. The spill was contained, but sensors in nearby Archie Creek showed some of the acidic water had migrated there, killing crabs and minnows, Townsend said.

“We had a monitoring system that found it, and our people were on it immediately,” Townsend said. He was not sure what caused the leak in the double-walled pipe.

Fred Nassar, compliance assurance manager for the Hillsborough County Environmental Protection Commission, said the agency issued a warning letter to Mosaic, which formerly was named Cargill.

“In our warning letter, we’re asking for details about the cause and what kind of corrective actions are being taken,” Nassar said.

Wednesday night’s leak pales compared with the 65 million gallons of acidic process water that spilled at the Cargill plant in September 2004. The spill happened when winds from Hurricane Frances generated waves that breached a dike on top of a phosphogypsum stack.