A warning has been issued to users of a popular South West swimming spot that an amoeba within the water could cause a rare but fatal disease.

Although the bacteria-feeding amoeba naegleria, which was found in the water at Black Diamond near Collie, is not dangerous by itself, rising temperatures could see it mutate into naegleria fowleri which can cause the untreatable brain disease amoebic meningitis.

Black Diamond is a popular swimming spot for Collie locals and tourists. Credit:Collie Mail

The Shire of Collie released a statement confirming the presence of amoeba naegleria in the water at Black Diamond, a former open cut mine in Allanson the Shire of Collie which is used by locals and tourists as a recreational area.

"As a result of high use, illegal camping, low rainfall and community complaints, the Shire of Collie has been undertaking water quality sampling of the water in the Black Diamond mining void. During sampling, the organism amoeba naegleria has been detected in this water body," a spokesperson from the shire said.