A massive fish kill affecting 40 miles of the Ogeechee River was caused by a bacterial disease induced by environmental stress, environmentalists said Thursday.

However, questions are still unanswered about what caused the environmental stress.

“The cause of the environmental stress is still unknown; therefore, EPD continues to advise citizens in Bryan, Bulloch, Chatham, Effingham and Screven counties not to swim in or consume fish from the Ogeechee River until further notice,” said Kevin Chambers, an EPD spokesman who issued a press release around 6:30 p.m. Thursday, three hours after government officials held a briefing regarding the matter.

The bacterial disease, columnaris, caused lesions, tattered fins and death of thousands of fish of all kinds from a point about six miles north of the Hwy. 301 North landing in Bulloch County to locations about 40 miles south of that point. It is not known to affect humans, he said.

Ogeechee Riverkeeper Dianna Wedincamp said Thursday evening she still has questions about the fish kill, which she traced to a discharge pipe at King America Finishing, a textiles plant six miles north of the U.S. 301 bridge near Dover in Screven County.