It is believed a political party contesting the municipal by-elections in Metsimaholo allegedly submitted 5,000 names as special voters, more than 1,000 of which were found to be deceased.
The revelations were made by the South African Communist Party (SACP), which is contesting the elections against their alliance partner, the ANC.
In an interview with HuffPost, SACP spokesman Alex Mashilo said "an organisation" (he would not directly name the party involved) submitted 5,000 names as special voters in the election.
"It was discovered that at least 1,000 of them are deceased. Most of the others were people who no longer reside in those districts. We are asking what would be the motive [for] this?" Mashilo said.
Mashilo was defending his party's first deputy general secretary, Solly Mapaila, after the ANC released a statement earlier on Wednesday demanding that Mapaila provide "irrefutable evidence" to back his claims that vote rigging took place at the by-elections.
"Like all other parties contesting the by-elections, the ANC is represented in the Political Liaison Committee (PLC), which meets on a daily basis to ensure credible, free and fair elections," the ANC said.
"Following a PLC meeting this morning, we have received a report that no party lodged a complaint on irregularities of the voters roll and bussing in of people or voters. To this end, the ANC demands irrefutable evidence on the allegations made."
They have given the SACP a deadline of 2pm.
"After such submissions are made to the PLC, the ANC calls for a formal investigation by the Independent Electoral Commission (IEC) into the allegations made. We equally urge all contesting parties to refrain from making statements that falsely accuse other parties and that cannot be proved," it said.
But Mashilo said they have not received any correspondence from the ANC.
"We have not received any correspondence demanding any evidence. But if we do receive it, we will attend to it," he said.
The municipal by-elections in Metsimaholo mark the first time the SACP are going to head-to-head with the ANC in an election.
Independent Electoral Commission spokesperson Kate Bapela said PLCs are usually convened four times a day, and if there are any objections, they would be dealt with at those meetings.
"When it comes to matters of vote rigging, any contesting party will know the legal process of lodging an objection in the prescribed manner," Bapela said.
"It is unfortunate that such matters are brought to the media before the IEC can deal with it... Any matters will be dealt with in due process."