The state Department of Health is shutting down a beach on the south shore of Kauai for two months while it works to pinpoint the source of fecal matter that has polluted its nearshore waters for years.

Public access will be restricted starting Monday around Waiopili Ditch, a stream that runs through rural Mahaulepu. People play in the area where it dumps into the ocean.

Health officials said in a release Thursday that they will be conducting environmental sampling through Nov. 30 to study the bacteria in recreational waters at Waiopili Ditch and in the surrounding Poipu-Koloa Watershed area.

This is a follow-up to their test earlier this year that found high levels of enterococci bacteria. What the department doesn’t know is the exact cause.

The bacteria, a widely used indicator of fecal contamination, is found in animal and human intestines and can cause serious, even life-threatening diseases.

In its March report, the department blamed the fecal waste of feral pigs, sheep, rats, birds and possibly a dozen land tortoises for polluting a stream.

The Surfrider Foundation has been clamoring for years for the department to do something about the unsafe water levels.

“It is irrelevant at very high concentrations whether that is human waste or animal waste; it is still a public health risk,” Carl Berg, Surfrider’s Kauai chapter chair, said after the March study came out. The marine biologist and research scientist has been testing water quality on the Garden Isle for 20 years.

The U.S. Environmental Protection Agency has been pressuring the state Department of Health to do a better job of protecting the public’s health when it comes to unsafe levels of fecal-waste bacteria in the water.

“We feel vindicated that DOH has heeded our warnings about water quality conditions at Mahaulepu, which we’ve been monitoring for a while now,” Stuart Coleman, head of the Hawaii chapter of Surfrider, said Thursday.

The department is now working with the University of California’s Berkeley Lab to test water, sediment, soil, decaying leaves, injection well and cesspool effluent, and fecal matter from various animals and birds to identify specific sources of contamination.

“Restricting access to the area will help to ensure the accuracy of our sampling,” said Keith Kawaoka, state deputy director of the Environmental Health Administration.

Accessing the beach generally requires traversing Mahaulepu Farm’s land, so the state is working with the farm to close the area. Health officials say the closure won’t affect lease holders or tenants in the area.