At least six of the urine samples taken from school children have tested positive for bilharzia.
The Limpopo department of health and social development took urine samples from about 25 pupils, mostly boys, at Ramasodi Primary School in Makgophong village, near Zebediela, after many pupils fell ill last week.
The pupils had complained of several symptoms, including fever, diarrhoea and burning while passing urine. Others were urinating blood.
Department spokesman Elias Mugari said that further tests on other pupils had been intensified in an effort to control the spread of bilharzia.
"We have had at least six confirmed cases of bilharzia from the pupils and treated them immediately."
He urged people with the associative symptoms to quickly seek treatment, "be it at clinics, hospitals or any health institution" to control the disease.
School principal Lesiba Dikgale said the pupils swim in the nearby Nkumpi river, exposing themselves to the disease.
Mugari said they would continue to conduct educational health workshops in rural villages to teach communities about the dangers of using unpurified water.