Police have put a "red alert" on South Africa's borders to prevent any attempt by Zimbabwean first lady Grace Mugabe, accused of assaulting a model in a Johannesburg hotel, to flee the country.
Her husband, Zimbabwean president Robert Mugabe, has meanwhile arrived in South Africa for a regional summit, complicating the diplomatic dilemma confronting the government.
Ms Mugabe (52) has asked for diplomatic immunity in the case, but has not been charged. Her whereabouts were not known to the authorities on Thursday.
The alleged victim, model Gabriella Engels (20), has accused Ms Mugabe of barging into a hotel where Ms Engels was meeting with Mr Mugabe's sons, and whipping her with an electric cord.
Police minister Fikile Mbalula told reporters on Wednesday that Ms Mugabe had been due to appear in court on Tuesday afternoon under a deal struck with authorities, but failed to turn up.
On Thursday, Mr Mbalula said police had put a “red alert” for the first lady on South Africa’s borders.
“We had already put tabs on the borders, in relation to her leaving the country, so there’s no question about that,” he told reporters.
So far she had made no attempt to flee, he added.
The South African government has made no official comment on the case and foreign ministry spokesmen have not answered their phones for two days, but the issue is causing waves at the highest level.
Justice minister Michael Masutha said he was attending a meeting on Wednesday evening to discuss the matter.
The police have said Grace Mugabe will get no special treatment.
Former state prosecutor Gerrie Nel said the Engels family had been approached by a third party to accept a cash settlement to drop the case.
“The family is not interested in doing that,” said Mr Nel. “They said let us talk and make this go away. No amount was mentioned.”
Mr Nel, who laid out the murder case against track star Oscar Pistorius and is nicknamed "the Pitbull", told a news conference he was ready to represent Ms Engels. He said an investigator had told him police were preparing an arrest warrant for Ms Mugabe.
However, a senior police source said that was not the case.
“We are not preparing an arrest warrant yet,” the source said. “Our investigations were completed, but before we could take the next step, the suspect applied to invoke diplomatic immunity. We are waiting the outcome before we can move on to the next step.”
Debbie Engels, mother of the alleged victim, said: "Now I know that this woman is not going to get off scot free for what she did."