Speaking on 702 Talk Radio on Wednesday, a Musina resident said the town got its water from the Limpopo, and she said sewage was seeping into the river from Beitbridge, which, like many Zimbabwe towns, has no functioning water supply or sewage disposal.
Scores of people infected with cholera are being treated on the South African side of the border.
A caller to 702 said two Zimbaweans had died, although this was not confirmed by the provincial health authorities.
Many more are streaming continuously across the border via the border post and illegally in search of food and health care.
Cholera is raging across Harare, particularly its western areas, and hundreds have died, according the doctors in the city.
"Since Saturday we have received and treated a total of 68 cholera patients from Zimbabwe," said Phuti Seloba, spokesperson for the Limpopo Health Department in the town of Musina.
"Sixty-six of them are Zimbabweans, while two others are South Africans engaged in cross-border business. Only 14 of them are still in the hospital."
"We have set up a centre near the border to handle cases and to relieve the hospital. Not all patients need to visit a hospital to get treated for cholera," Seloba said.
Doctors Without Borders said on Tuesday that up to 1,4-million people in Zimbabwe were at risk of the water-borne disease.
The Zimbabwe Association of Doctors for Human Rights issued a grave warning yesterday that the public health system had collapsed and urgent action was needed to rescue it and prevent the worst cholera outbreak in living memory from spreading.
"The main referral hospitals in the country – Harare Central Hospital and Parirenyatwa Hospital, in Harare, and Mpilo Hospital and United Bulawayo Hospital, in Bulawayo, have been closed. Most district hospitals and municipal clinics are barely functioning or are closed," the association said.
"Health workers have continued to attempt to deliver health services in extremely difficult circumstances and planned to march to the offices of the minister of health and child welfare to present a petition calling for urgent action to be taken to restore accessible and affordable healthcare to Zimbabwe’s population."
The doctors called on the government to declare the cholera outbreak a national disaster and called on President Robert Mugabe to "solicit international support to bring it under control and restore the supply of safe water and sanitation".
They also called for drugs and equipment to be provided urgently.