The disaster occurred in the diamond mining town of Jagersfontein, forcing officials to evacuate scores of residents to nearby farms.
The flooding damaged cellphone towers, hitting communications, and affected drinking water, while some roads were cut off.
(Twitter/@mzwakhe_masilo)
Flooding caused by the collapse of a mine dam wall in South Africa's Free State province has swept away houses and cars, killing at least one person and injuring 40.
Television footage showed a river of mud and water flowing away from the disused diamond mine and into a nearby residential area on Sunday.
It covered roads and swept houses away in Jagersfontein, a town about 100 kilometres (62 miles) southwest of the Free State province capital Bloemfontein.
"A mine dam collapsed and swept away houses and cars in the area," said Palesa Chubisi, a spokesperson for Free State premier Sisi Ntombela.
At least one person was killed, but the overall death toll was unclear.
Free State authorities initially said three bodies had been recovered but later revised the figure down to one.
Mineral and energy resources minister Gwede Mantashe said there were up to five suspected deaths, four people missing and another four in critical conditions.
"Nine houses were swept away and 20 houses completely damaged. Now, that is a disaster," Mantashe told an online press conference.
Earlier, Chubisi said 40 people including a pregnant woman were taken to local hospitals, four suffering from fractured limbs and the rest with bruises and hypothermia.
South Africa | Posted Today by Arrive Alive. Mine dam wall collapsed near Jagersfontein
Search and rescue underway
Search and rescue operations at the scene were ongoing, with people in affected areas being evacuated to nearby farms, authorities said.
"The reports received thus far is that the flow of the water has ceased and the immediate threat is being stabilised," said Nkosazana Dlamini-Zuma, the minister in charge of disaster management.
An aid group with staff at the scene said "thousands of litres of sludge" poured out of the dam onto nearby communities.
"Houses, personal belongings and many sheep have been washed away," the Gift of the Givers NGO said on Facebook.
"The cellphone towers have been damaged affecting communication, there is no electricity and not a drop of drinkable water. Some of the roads have been cut off."
National electricity utility Eskom said Jagersfontein was left without power after one of its substations was "engulfed by the mud".
"Due to the current situation in the Jagersfontein area and inaccessibility of our substation, it is impossible to estimate when supply will be restored or to determine the extent of the damage," Eskom said.
Once owned by diamond mining giant De Beers, the mine was acquired by Superkolong Consortium in 2010, according to the government, which described it as now "abandoned".
The Minerals Council South Africa industry group said the mine, which is not currently owned by any of its members, was shut in the 1970s.
The flooding caused some houses to collapse "leading some members of the community to escape with only the clothes on their backs", said the provincial department of social development, which was helping with evacuation and relief efforts.
A disaster management team was at the scene to determine the extent of the damage, but the cause was not yet known.
Source: TRTWorld and agencies
