Adetshina’s announcement that she would not take part in Saturday’s final came a day after the Home Affairs ministry accused her mother of fraud and identity theft.
“After much careful consideration, I have made the difficult decision to withdraw myself from the competition for the safety and wellbeing of my family and I,” Adetshina, 23, wrote on Instagram.
Adetshina, a law student, has been the subject of vicious, xenophobic attacks on social media since she was announced as a finalist in July, with many – including cabinet ministers – questioning her credentials because of her Nigerian descent.
The ruckus led to an investigation into her citizenship by the home affairs ministry, after a request from the pageant’s organisers.
This uncovered “prima facie indications” that Adetshina’s mother may have committed fraud and stolen the identity of a South African woman after the Miss SA hopeful was born, the ministry said on Wednesday.
“Reasons exist to believe that fraud and identity theft may have been committed by the person recorded in home affairs records as Chidimma Adetshina’s mother,” said the home affairs minister, Leon Schreiber.
“An innocent South African mother, whose identity may have been stolen as part of the alleged fraud committed by Adetshina’s mother, suffered as a result because she could not register her child.”
The ministry said it was obtaining legal advice on the implications on Adetshina’s citizenship, adding the contestant did not participate in the alleged unlawful actions as she was an infant at the time.
Adetshina and her mother had given their written consent to the initial investigation, it said.
The investigation has broadened to identify and pursue any officials involved in the alleged fraudulent scheme, the ministry said, adding it “deployed every resource at its disposal to establish the truth”.
The organisers of Miss South Africa did not immediately reply to a request for comment.
They had previously said that Adetshina, a law student, was a South African citizen holding “both a South African ID and passport” and thus met all the contestant eligibility criteria.
Adetshina had previously told local media she was born in Soweto to a Nigerian father and a South African mother of Mozambican descent.
South Africa grants citizenship by birth to anyone born in the country after 1995. Adetshina was born in 2001.
Her participation in the pageant has stoked anti-foreigner sentiment in the nation, which has witnessed violent, and at times deadly, attacks on immigrants in the past.
Politicians, celebrities and ordinary citizens have weighed in on the debate on social media and chatshows.
While many came to her defence, others argued she should be disqualified over her Nigerian ties.
Among the loudest critics was the arts and culture minister, Gayton McKenzie, whose far-right party won 2% of the vote in the May general election in which immigration was a key issue.
Hostility towards foreigners has increased in recent years, as South Africans tire of unwavering unemployment.
Despite lacklustre economic growth, the continent’s most industrialised nation attracts millions of migrants, mainly people from other African countries.